LIGO/Virgo S190425z

N. P. M. Kuin (UCL-MSSL), A. A. Breeveld (MSSL-UCL),  C. Gronwall (PSU),
F. E. Marshall (NASA/GSFC), S. R. Oates (Uni. of Warwick), M.J. Page
(UCL-MSSL),
M. de Pasquale (U Istambul), M. H. Siegel (PSU), A. D'Ai (INAF-IASFPA),
P. D'Avanzo (INAF-OAB), S. D. Barthelmy (NASA/GSFC), A. P. Beardmore (U.
Leicester),
D. N. Burrows (PSU), S. Campana (INAF-OAB), S. B. Cenko (NASA/GSFC),
G. Cusumano (INAF-IASF PA), V. D'Elia(ASDC), P. A. Evans (U. Leicester),
P. Giommi (ASI), D. Hartmann (Clemson U.), J. A. Kennea (PSU),
H. A. Krimm (NSF), A. Y. Lien (GSFC/UMBC), D. B. Malesani (DARK/NBI),
A. Melandri (INAF-OAB), J. A.  Nousek (PSU), P. T. O'Brien (U. Leicester),
J. P. Osborne (U. Leicester), C. Pagani (U. Leicester), K. L. Page
(U.Leicester),
D.M. Palmer (LANL), M. Perri (ASDC), J. L. Racusin (NASA/GSFC), T. Sakamoto
(AGU),
B. Sbarufatti (INAF-OAB/PSU), G. Tagliaferri (INAF-OAB), A. Tohuvavohu
(PSU),
and E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift team:

The Neil Gehrels Swift Observatory UVOT and XRT instruments began pointed
galaxy-targeted followup of the LIGO/Virgo detected S190425z (LVC GCN.
24168)
at 2019-04-25 12:53 UT (T0+274 min), delayed due to a commanding gap.
The observations continued until 2019-04-26 20:15 UT, when they were aborted
to begin followup of S190426c (LVC GCN. 24237).

The UVOT points at the same sky area as the Swift XRT but with a slightly
smaller FOV (17'x17'). As announced in Tohuvavohu et al.
(GCN Circ. 24353
Loading...
 
  ), the Swift GW follow up can be seen at
http://www.swift.ac.uk/LVC/.

The Swift UVOT exposures of around 70s are usually in the u-band (central
wavelength 350nm) or a UV band when there are bright stars in the FOV. The
nominal exposure time varies depending on several factors like the slew
time.
The limiting magnitude can vary but typically is 18.6th magnitude.

Each field is automatically processed by detecting sources in the image,
matching them to several catalogs and screening the remaining sources to
remove artifacts.  A check is made for any remaining candidates against the
Minor Planet Center list of solar system objects. Candidates are ranked for
further examination. In addition, for each galaxy detected in the UVOT image
which is in the GLADE catalog, a "postage stamp" image of a small region
around
the galaxy is produced as well as a comparison "postage stamp" from the
DSS to be used for manual inspection.

After the automated processing, potential candidates are all examined
manually.
This allows for the removal of image artifacts from our candidate lists
that
sometimes get flagged as potential sources. For S190425z the automated
processing
identified 21 source candidates which all, except for one, were either
image
artifacts or fast moving objects that passed the screening.

A further examination of the "postage stamps" with galaxies is then made as
effort allows. This is done mainly because the source-finding algorithm
has difficulty finding point sources in extended sources such as galaxies.

For the fields observed for S190425z, 2298 galaxy postage stamp images were
generated. No credible sources were found.

The candidate source reported in Breeveld et al. (GCN Circ. 24296
Loading...
 
 ) was
identified
initially by the automated processing, and is likely a very red flaring
object
(see also Lipunov et al. GCN Circ. 24326
Loading...
 
 ).

B. Gendre (OzGrav-UWA), C. Lachaud (APC), V. Aivazyan (Iliauni), K. 
Barynova (Kyiv Uni), A. Burrel (OzGrav-UWA), B. Chabert (OzGrav-UWA), H. 
Crisp (OzGrav-UWA), D.Coward (OzGrav-UWA), E. Howell (OzGrav-UWA), A. N. 
Klotz (UPS), J. Moore (OzGrav-UWA), S. Antier (APC), S. Basa (LAM), M. 
Boer (Artemis), D. Corre (LAL), M. Coughlin (Caltech), J.G. Ducoin 
(LAL), P. Hello (LAL), A. Klotz (IRAP), N. Leroy (LAL), D. Turpin 
(NAOC), X. Wang (THU),

report on behalf of the Zadko Telescope team and GRANDMA collaboration;

We performed tiled observations of LIGO/Virgo BNS event S190425z with 
the Zadko telescope, using a clear filter.

The observation started on 04/25/19 14:56:19 UTC which corresponds 
approximately to 6.65 hours after the GW trigger time. However, due to 
hardware issues, the first images of interest were obtained the next day 
(04/26/19, 14:19:00 UTC)

We performed the following observations in galaxy targeting mode:

   R.A.      DEC.
16:57:53 -01:56:51
16:57:38 -01:48:37
16:57:07 -01:52:10
16:04:51 +24:03:15
16:04:32 +23:55:05

We have not found any credible counterpart candidate, down to R ~ 16.

The Zadko team acknowledges support from the OzGrav Centre of Excellence 
of the Australian Research Council. GRANDMA (Global Rapid Advanced 
Network Devoted to the Multi-messenger Addicts) is a network of robotic 
telescopes connected all over the world with both photometry and 
spectrometry capabilities for Time-domain Astronomy 
(https://grandma.lal.in2p3.fr/).

---
L'absence de virus dans ce courrier ��lectronique a ��t�� v��rifi��e par le logiciel antivirus Avast.
https://www.avast.com/antivirus

D. A. Kann (HETH/IAA-CSIC), C. Thoene (HETH/IAA-CSIC), C. Stachie 
(Artemis), X. Zhang (THU), Z. Vidadi (Shao), M. Blazek (HETH/IAA-CSIC), 
K. Bensch (HETH/IAA-CSIC), L. Izzo (HETH/IAA-CSIC), A. de Ugarte Postigo 
(HETH/IAA-CSIC, DARK/NBI), S. Antier (APC), S. Basa (LAM), M. Boer 
(Artemis), D. Corre (LAL), M. Coughlin (Caltech), D. Coward 
(OzGrav-UWA), J.G. Ducoin (LAL), B. Gendre (OzGrav-UWA), P. Hello (LAL), 
A. Klotz (IRAP), C. Lachaud (APC), N. Leroy (LAL), D. Turpin (NAOC), and 
X. Wang (THU)

report on behalf of the HETH group and GRANDMA collaboration:

We observed the location of the Swift UVOT transient (Breeveld et al., 
GCN #24296
Loading...
 
 ) discovered in the error region of the aLIGO/Virgo Binary 
Neutron Star merger event S190425z (Ligo Scientific Collaboration and
VIRGO Collaboration, GCN #24168
Loading...
 
 , #24228
Loading...
 
 ), with 
the 2.2m CAHA telescope and CAFOS. We obtained 3 x 240 s each in U/B and 
6 x 120 s in V/Rc/Ic. The observations were performed on 2019-04-28 from 
02:11:50 to 03:52:47 UT.

At the position (Palmese et al., GCN #24312
Loading...
 
 ) of the likely counterpart 
(thought to be an M2 dwarf that had a powerful flare which UVOT 
detected, Lipunov et al., GCN #24326
Loading...
 
 ; Bloom et al., GCN #24337
Loading...
 
 ), we 
detect a source in Rc and Ic and derive the following upper limits and 
magnitudes:

U > 22.9 mag;
B > 23.5 mag;
V > 23.5 mag;
Rc = 22.51 +/- 0.15 mag (depth Rc > 23.8 mag);
Ic = 21.53 +/- 0.15 mag (depth Ic > 22.9 mag).

Magnitudes are given in the AB system and were obtained vs. a comparison 
star from PanSTARRS and the transformations of Lupton (2005).

Our detections are in reasonable agreement with other reports (Palmese 
et al., GCN #24312
Loading...
 
 ; Bloom et al., GCN #24337
Loading...
 
 ; Hu et al., GCN #24324
Loading...
 
 ) and 
indicate the source was quiescent during our observations.

GRANDMA (Global Rapid Advanced Network Devoted to the Multi-messenger 
Addicts) is a network of robotic telescopes connected all over the world 
with both photometry and spectrometry capabilities for Time-domain 
Astronomy (https://grandma.lal.in2p3.fr/).

This message may be cited.

[GCN OPS NOTE(12jun19), The second reference in the first paragraph
was changed from "Breeveld et al., #24296" to
"Ligo Scientific Collaboration and VIRGO Collaboration, GCN #24168
Loading...
 
 , #24228
Loading...
 
 ".]

D. Svinkin, S. Golenetskii, R.Aptekar, D. Frederiks,
M. Ulanov, A. Tsvetkova, A. Lysenko, A. Kozlova, and T. Cline,
on behalf of the Konus-Wind team, report:

Konus-Wind (KW) was observing the whole sky at the time of the
LIGO/Virgo event S190425z (2019-04-25 08:18:05.017 UTC, hereafter T0;
LIGO/Virgo Collaboration GCN Circ. 24168
Loading...
 
 ).

No triggered KW event happened from ~6 days before and ~2 days
after T0. The closest waiting-mode event was ~0.5 days before T0.
Using waiting-mode data within the interval T0 +/- 100 s,
we found no significant (> 5 sigma) excess over the background
in both KW detectors on temporal scales from 2.944 s to 100 s.

We estimate an upper limit (90% conf.) on the 20 ��� 1500 keV fluence
to 9.0x10^-7 erg/cm^2 for a burst lasting less than 2.944 s and having a
typical KW short GRB spectrum (an exponentially cut off power law with
alpha =-0.5 and Ep=500 keV). For a typical long GRB spectrum (the Band
function with alpha=-1, beta=-2.5, and Ep=300 keV), the corresponding
limiting peak flux is 2.7x10^-7 erg/cm^2/s (20 ��� 1500 keV, 2.944 s scale).

All the quoted values are preliminary.

LIGO/Virgo S190425z: Insight-HXMT observation and counterpart search

J. Guan, Y. Nang, N. Sai, C, Wang, C. K. Li, J. Y. Liao, Y. Huang, Y. J. Yang, Z. W. Li, X. B. Li, G. Li, S. L. Xiong, L. Tao, C. Z.
+Liu, X. L. Cao, Y. Chen, A. M. Zhang, Y. J. Jin, Z. Zhang (THU), T. P. Li (IHEP/THU), F. J. Lu, L. M. Song, M. Wu, Y. P. Xu, S. N.
+Zhang (IHEP), report on behalf of the Insight-HXMT team:

We performed small area scan survey of the LIGO localization region with Insight-HXMT after the LVC trigger S190425z (LVC et al. GCN
+24168). The observation started at 2019-4-25 16:28 UTC, about 8 hours after the trigger time. Four fields were visited, with
+overlaps, mapping 987.2 square degrees of the bayestar map 90% credible region and covering a sky region totalling of 20.4% of the
+LIGO localization likelihood. Each field was scanned twice and the total exposure time was 79.2 ks. No significant new source is
+found in the region in search of the Insight-HXMT raw light curves.


The survey also covered T2019ebq/PS19qp (Smith et al. GCN, 24210), a possible optical counterpart to S190425z, at 2019-04-26 02:12
+UTC (for 400s) and 2019-04-26 15:06 UTC (for 250s). We find no significant new X-ray sources in the data. The 5-sigma flux upper
+limits are obtained when fitting the light curves to the position of T2019ebq/PS19qp: 6.8 mCrab (HE���25-100 keV), 16.2 mCrab
+(ME���7-40 keV) and 5.2 mCrab (LE���1-6 keV). The flux upper limits for other positions in the scanned fields are about the same as
+quoted above.

Further analysis will be reported in the following circulars.

Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA)
+and the Chinese Academy of Sciences (CAS). More information could be found at: http://www.hxmt.org.


List of observed fields:

Start (UTC)        RA and Dec (J2000)   radius(degree)
2019/4/25 16:28    245    20         10
2019/4/25 19:38    252    12         10
2019/4/25 22:49    235    30         10
2019/4/26 02:00    255    0          10
2019/4/26 05:11    245    20         10
2019/4/26 08:22    252    12         10
2019/4/26 11:33    235    30         10
2019/4/26 14:44    255    0          10


--

Sincerely Yours,
Zhengwei Li,
Key Laboratory of Particle Astrophysics,
Institute of High Energy Physics,
Chinese Academy of Sciences, Beijing China
TEL:15210983070 E-mail:lizw@ihep.ac.cn

J. Vinko, A. Bodi, L. Kriskovics, K. Sarneczky and A. Pal (Konkoly Observatory) report additional CCD imaging of potential host galaxies of S190425z targeted by the Hobby-Eberly Telescope VIRUS spectrograph (GCN #24175
Loading...
 
 ). CCD frames were taken with the 0.6/0.9m Schmidt telescope (FoV 70x70 arcmin^2, unfiltered, limiting mag ~21.5) and the 0.8m RC telescope (FoV 18x18 arcmin^2, g- and r-band, limiting mag r~20.4) between 2019-04-25.9 and 2019-04-26.0 UT. The frames were centered at the following positions: 

241.236267 +23.932871 = 16:04:56.7 +23:55:58:33 
247.400574 +15.65844 = 16:29:36.1 +15:39:03.38 
253.245255 +2.400985 = 16:52:58.8 +02:24:03.06 
254.505371 -1.822693 = 16:58:01.2 -01:49:20.17 
254.780334 -5.741986 = 16:59:07.2 -05:44:31.14 

The deepest unfiltered frames were compared to PS1 templates applying image subtraction. 

No new transient source has been found on either frames down to the limiting magnitude of ~ 21.5 listed above.

Z. Kostrzewa-Rutkowska (SRON/RU), S. Hodgkin, A. Delgado, D.L. Harrison, M.
van Leeuwen, G. Rixon, A. Yoldas (IoA Cambridge), D. Eappachen, P.G. Jonker
(SRON/RU) on behalf of Gaia Alerts team report the discovery of transient
candidates within the probability skymap of S190425z (LIGO/VIRGO
Collaboration GCN 24168
Loading...
 
 ):

---------------------------------------------------------------------------

Name      TNSid Date [TCB]          RaDeg DecDeg AlertMag URL

---------------------------------------------------------------------------

Gaia19bqf AT2019eiu
Loading...
 
  2019-05-01T09:54:18 50.39901 -52.89803  18.81

      http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19bqf/

Gaia19bqe AT2019eit
Loading...
 
  2019-04-30T17:13:48 20.70267 -38.78741  18.76

      http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19bqe/

Gaia19bqd AT2019eis
Loading...
 
  2019-04-30T15:41:20 32.80392 -48.59636  18.68

      http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19bqd/


---------------------------------------------------------------------------


Acknowledgements: This work has made use of data from the European Space
Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by
the Gaia Data Processing and Analysis Consortium (DPAC,
https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC
has been provided by national institutions, in particular the institutions
participating in the Gaia Multilateral Agreement. ZKR, DE, and PGJ
acknowledge support from the European Research Council under ERC
Consolidator Grant agreement no 647208.

Z. Kostrzewa-Rutkowska (SRON/RU), S. Hodgkin, A. Delgado, D.L. Harrison, M.
van Leeuwen, G. Rixon, A. Yoldas (IoA Cambridge), D. Eappachen, P.G. Jonker
(SRON/RU) on behalf of Gaia Alerts team report the discovery of a transient
candidate within the probability skymap of S190425z (LIGO/VIRGO
Collaboration GCN 24168
Loading...
 
 ):

---------------------------------------------------------------------------

Name      TNSid Date [TCB]          RaDeg DecDeg AlertMag URL

---------------------------------------------------------------------------

Gaia19bpw AT2019eig
Loading...
 
  2019-04-29T15:15:23 9.92876 -31.99236 18.54
http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19bpw/


---------------------------------------------------------------------------



Acknowledgements: This work has made use of data from the European Space
Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by
the Gaia Data Processing and Analysis Consortium (DPAC,
https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC
has been provided by national institutions, in particular the institutions
participating in the Gaia Multilateral Agreement. ZKR, DE, and PGJ
acknowledge support from the European Research Council under ERC
Consolidator Grant agreement no 647208.

G. Dimitriadis, D. O. Jones, M. R. Siebert, J. S. Brown (UCSC),
I. Arcavi (Tel Aviv University), J. S. Bloom (UC Berkeley),
K. A. Bostroem (UC Davis), D. A. Coulter (UCSC), M. R. Drout (University of Toronto),
H. Ebeling (IfA-Hawaii), A. V. Filippenko (UC Berkeley), R. J. Foley (UCSC),
D. A. Howell (LCO/UCSB), T. Hung (UCSC), S. W. Jha (Rutgers), D. Kasen (UC Berkeley),
C. D. Kilpatrick (UCSC), A. L. Piro (Carnegie Obs.), J. X. Prochaska (UCSC),
E. Quataert (UC Berkeley), E. Ramirez-Ruiz (UCSC), A. G. Riess (STSci),
C. Rojas-Bravo (UCSC), D. J. Sand (UA), D. M. Scolnic (Duke), K. Siellez (UCSC),
S. Valenti (UC Davis) and W. Zheng (UC Berkeley).

We obtained near-IR spectroscopy of PS19qp (= AT 2019ebq
Loading...
 
 ) (GCN #24210
Loading...
 
 ), a proposed
counterpart to the gravitational wave event S190425z (GCN #24168
Loading...
 
 ), with the 
Multi-Object Spectrometer For Infra-Red Exploration (MOSFIRE) on the Keck I telescope
on Mauna Kea, starting at UT 2019-04-26 14:32:11, aproximately 1.2 days after
the LIGO/Virgo alert.

Our spectrum covers the J-band (1.15-1.35 microns). Visual inspection of the spectrum
indicates it is consistent with Type Ic supernovae a few days prior to maximum light,
similar to previous spectroscopic classifications (GCN #24230
Loading...
 
 , GCN #24233
Loading...
 
 , GCN #24252
Loading...
 
 ).

We thank the staff of Keck observatory, especially Josh Walawender,
for facilitating this Target of Opportunity observation.

Igor Andreoni (Caltech), Eric Bellm (UW) report on behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations

 

We searched for Zwicky Transient Facility (ZTF) detections associated with Gaia19bpt AT2019ehz
Loading...
 
  (Kostrzewa-Rutkowska et al., GCN 24354
Loading...
 
 ) in the archive of ZTF alerts. ��A source, dubbed ZTF19aarioci, was found varying at the location of Gaia19bpt.�� The source was first detected in ZTF data on 2019-04-21 (g ~ 19.8), with detections in the public surveys beginning on 2019-04-23.

 

The optical event was detected days before the gravitational wave trigger S190425z (LIGO and Virgo Collaboration, GCN 24168
Loading...
 
 ), therefore we exclude an association between Gaia19bpt AT2019ehz
Loading...
 
  and S190425z. 

 

ZTF and GROWTH are worldwide collaborations comprising Caltech, USA; IPAC, USA, WIS, Israel; OKC, Sweden; JSI/UMd, USA; U Washington, USA; DESY, Germany; MOST, Taiwan; UW Milwaukee, USA; LANL USA; Tokyo Tech, Japan; IIT-B, India; IIA, India; LJMU, UK; TTU USA and USyd, Australia. ZTF acknowledges the generous support of the NSF under AST MSIP Grant No 1440341. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019).

Z. Kostrzewa-Rutkowska (SRON/RU), S. Hodgkin, A. Delgado, D.L. Harrison, M.
van Leeuwen, G. Rixon, A. Yoldas (IoA Cambridge), D. Eappachen, P.G. Jonker
(SRON/RU) on behalf of Gaia Alerts team report the discovery of transient
candidates within the probability skymap of S190425z (LIGO/VIRGO
Collaboration GCN 24168
Loading...
 
 ):

---------------------------------------------------------------------------

Name      TNSid Date [TCB]          RaDeg DecDeg AlertMag URL

---------------------------------------------------------------------------

Gaia19bpt AT2019ehz
Loading...
 
  2019-04-29T06:51:22 212.42448 55.49114 18.49
http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19bpt/
Gaia19bps <http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19bpt/%0DGaia19bps>
AT2019ehy
Loading...
 
  2019-04-28T22:13:01 80.97925 -67.87885 15.78

http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19bps/

Gaia19bpr AT2019ehx
Loading...
 
  2019-04-29T04:14:24 83.92087 -66.86490 14.19

      http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19bpr/


---------------------------------------------------------------------------

Notes:
Gaia19bpt - galaxy SDSS J140941.88+552928.1 brightens by 2 mag
Gaia19bps - blue source brightens by 0.4 mag
Gaia19bpr - HMXB RX J0535.6-6651 brightens by 1 mag



Acknowledgements: This work has made use of data from the European Space
Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by
the Gaia Data Processing and Analysis Consortium (DPAC,
https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC
has been provided by national institutions, in particular the institutions
participating in the Gaia Multilateral Agreement. ZKR, DE, and PGJ
acknowledge support from the European Research Council under ERC
Consolidator Grant agreement no 647208.

Marc A. Murison, U.S. Naval Observatory--Flagstaff Station (NOFS)

We imaged the position of the reported Swift/UVOT transient (Breeveld
et al., GCN Circ. 24296
Loading...
 
 ), potentially corresponding to LIGO/Virgo trigger
S190425z (LIGO/Virgo Collaboration, GCN Circ. 24168
Loading...
 
 ), with the NOFS
1.3-meter telescope. Nine 900-second exposures were taken in SDSS r (5)
and g (4). Examination and comparison to PS1 reveals no new sources
brighter than apparent SDSS r magnitude 22.3. Exposure times were
2019-04-28 08:44 to 11:12 UTC. Stacking images did not produce benefit
due to variable and worsening seeing.

Z. Kostrzewa-Rutkowska (SRON/RU), S. Hodgkin, A. Delgado, D.L. Harrison, M.
van Leeuwen, G. Rixon, A. Yoldas (IoA Cambridge), D. Eappachen, P.G. Jonker
(SRON/RU) on behalf of Gaia Alerts team report the discovery of a transient
candidate within the probability skymap of S190425z (LIGO/VIRGO
Collaboration GCN Circ. 24168
Loading...
 
 ):

---------------------------------------------------------------------------

Name      TNSid Date [TCB]          RaDeg DecDeg AlertMag URL

---------------------------------------------------------------------------

Gaia19bpf AT2019egx
Loading...
 
  2019-04-28T17:04:25 8.95631 -35.89300  14.38

      http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19bpf/

---------------------------------------------------------------------------


Note: outburst of candidate CV ASASSN-14da


Acknowledgements: This work has made use of data from the European Space
Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by
the Gaia Data Processing and Analysis Consortium (DPAC,
https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC
has been provided by national institutions, in particular the institutions
participating in the Gaia Multilateral Agreement. ZKR, DE, and PGJ
acknowledge support from the European Research Council under ERC
Consolidator Grant agreement no 647208.

Tomas Ahumada (UMD), Michael W. Coughlin (Caltech),  Kai Staats
(Northwestern), Kevin Burdge (Caltech), Richard G. Dekany (Caltech), Dmitry
A. Duev (Caltech), Michael Feeney (Caltech), S. R. Kulkarni (Caltech), Reed
Riddle (Caltech) on behalf of the KPED team and the Global Relay of
Observatories Watching Transients Happen (GROWTH) collaboration.

We used the Kitt Peak EMCCD Demonstrator (KPED) on the Kitt Peak 84-inch
telescope (Coughlin et al 2019b) to obtain 300 s r-band images for ZTF
optical transients listed in Kasliwal et al. (GCN 24191
Loading...
 
 ) and Anand et al.
(GCN 24311
Loading...
 
 ) starting at 3:56:56.876 UT on 2019-04-28.

The measurements of ZTF19aasckkq are consistent with Malesani et al. (GCN
24319
Loading...
 
 ) and Ahumada et al. (GCN 24320
Loading...
 
 ). The object ZTF19aasbphu shows a
slight decrease in the r magnitude (r~-0.3) with respect to Anand et al.
(GCN 24311
Loading...
 
 )

We report upper limits for the rest of the transients. Magnitudes are
derived after calibrating against PS1:

 ID            JD RA         DEC magnitude

ZTF19aasckkq 2458602.473900463 248.4131017 13.9101828 g = 20.7 +- 0.2

ZTF19aasckkq 2458601.7544584144 248.4131017 13.9101828 r = 20.2 +- 0.1

ZTF19aasckkq 2458602.474675926 248.4131017 13.9101828 r = 20.1 +- 0.1

ZTF19aasckkq 2458601.7452688077 248.4131017 13.9101828 I = 19.4 +- 0.3

ZTF19aasckkq 2458601.750166088 248.4131017 13.9101828 I = 19.4 +- 0.3

ZTF19aasbphu 2458601.7107427316 245.5831354 21.4081853 r = 19.47 +- 0.2

ZTF19aasejil 2458601.8664184026 261.9458106 1.6537207 r > 20.8

ZTF19aasbamy 2458601.664547176 231.2656676 24.9275799 r > 20.4

ZTF19aascxux 2458601.8588976967 258.2933102 17.2938689 r > 20.3

ZTF19aasfogv 2458601.8632696294 261.8430161 -11.3338523 r > 19.9

ZTF19aarycuy 2458602.4741666666 244.0832363 21.7409257 r > 19.9

More observations for this objects are scheduled.

The KPED team thanks the National Science Foundation, the Caltech Space
Innovation Council, the National Optical Astronomical Observatory and the
Murty family for support in the building and operation of KPED.

V. Lipunov, N.Tyurina, E. Gorbovskoy, V.Kornilov, D.Vlasenko, V.Vladimirov, 
D.Zimnukhov, A.Kuznetsov, P.Balanutsa, I.Gorbunov, A. Chasovnikov, 
V.Grinshpun, F.Balakin, A.Chasovnikov (Lomonosov Moscow State University, SAI, 
Physics Department),

R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres (The 
Instituto de Astrofisica de Canarias),

R. Podesta, C. Lopez, C.Francile, F. Podesta (Observatorio Astronomico  Felix 
Aguilar OAFA, San Juan National University),

H.Levato (Instituto de Ciencias Astronomicas, de la Tierra y del Espacio 
ICATE,SJNU)

D. Buckley (South African Astronomical Observatory),

O. Gress, N.M. Budnev, O.Ershova (Applied Physics Institute, Irkutsk State 
University),

V. Yurkov, A. Gabovich, Yu. Sergienko, D. Kobcev (Blagoveschensk EducationState 
University),

A. Tlatov, V.Senik, A.V. Parhomenko, D. Dormidontov (Kislovodsk Solar  Station 
of the Pulkovo Observatory),

Global MASTER-Net (http://observ.pereplet.ru, Lipunov et al., 2010, Advances in 
Astronomy, vol. 2010, 30L)   started inspect of the LIGO/Virgo S190425z 
errorbox (Singer et al. GCN 24168
Loading...
 
 ) 3133 sec after trigger time at 2019-04-25 
09:10:18 UT  (Lipunov et al. GCN 24167
Loading...
 
 ).

After reviewing 25% of total probability, we found several possible 
transients. The most interesting is the MASTER OT J155829.22+271714.6.
Most likely this flash is related to the activity of the galaxy nuclear. 
Too large  redshift s = 0.09 (distance ~380 Mpc) excludes OT from possible 
candidates for a gravitational-wave event LIGO/Virgo S190425z.


MASTER OT J155829.22+271714.6  - Optical Flare in Active Seyfert Galaxy


MASTER-IAC (Teide Observatory, IAC, Tenerife, Spain) auto-detection system 
discovered OT source at (RA, Dec) = 15h 58m 29.22s +27d 17m 14.63s
2019-04-25 23:42:39.4 UT.
The OT unfiltered magnitude is 18.4m (limit 19.7 m).
  There is no minor planet at this place.
The discovery, referenceand differences images are available at
http://observ.pereplet.ru/images/MASTEROTJ155829.22+271714.6.jpg

The message may be cited.

Joshua S. Bloom (UC Berkeley), Catherine Zucker (Harvard), Eddie Schlafly
(LBNL), Doug Finkbeiner (Harvard), Jorge Mart��nez-Palomera (UC Berkeley),
Daniel A. Goldstein (Caltech), and Igor Andreoni (Caltech) report:

"Starting at 2019-04-28 5:10 UTC, we observed the region of the UVOT
transient (Breeveld et al. GCN #24296
Loading...
 
 ) candidate counterpart of the
gravitational wave event S190425z (LIGO/VIRGO Collaboration, GCN #24168
Loading...
 
 )
with the Victor M. Blanco 4m Telescope at Cerro Tololo Inter-American
Observatory, equipped with the Dark Energy Camera (DECam). We observed in
four bands (g for 6 minutes, r for 6 minutes, i for 8 minutes, z for 8
minutes).

Consistent with previous reports (Kong et al. GCN #24301
Loading...
 
 , Arcavi et al. GCN
#24307
Loading...
 
 , Im et al. GCN #24318
Loading...
 
 , Shappee et al. GCN #24313
Loading...
 
 , Hu et al. GCN
#24324
Loading...
 
 , Chang et al. GCN #24325
Loading...
 
 , Morihana et al. GCN #24328
Loading...
 
 , Tanvir et al.
GCN #24334
Loading...
 
 , Troja et al. GCN #24335
Loading...
 
 ), in 1.2 arcsec seeing, we find no
source at the reported position of the UVOT source, placing the following
upper limits, calibrated to PS1 photometry (Chambers et al. 2016,
arXiv:1612.05560
Loading...
 
 C):

  g > 24.0
  r > 24.0
  i > 23.7
  z > 23.1

The nearby source noted in Palmese et al. (GCN #24312
Loading...
 
 ) at position
ra=17:02:19.19, dec=-12:29:07.3 is detected in r, i, z and not detected in
g. We report the following magnitudes for this source:

  z = 21.50
  i = 22.04
  r = 23.03
  g > 24.0

All detection magnitudes inhere a ~0.1 mag uncertainty currently. The
r-band detection is consistent with Palmese et al. (GCN #24312
Loading...
 
 ) and thus
does not appear to be variable between the two observations. We find no
evidence for any spatial extent beyond the stellar PSF. The photometric
measurements (albeit not corrected for the Galactic extinction along the
line of sight) suggest the source to be a M2-dwarf star (see West et al.,
2011).

The currently reported astrometric location of the bright UV transient is
not precisely consistent with the location of the source discussed above.
However, if they are indeed physically associated (through a refined
astrometric study, especially since the UVOT source appears trailed) a
consistent picture emerges: the UVOT detection was due to a flare from an
M2-dwarf star in our galaxy. We thus agree with the hypothesis advanced by
Lipunov et al. (GCN #24326
Loading...
 
 ) that the UVOT event is unrelated to GW
S190425z."

This message may be cited.

Eleonora Troja (GSFC/UMD), Alan M. Watson (UNAM), Rosa L. Becerra (UNAM),
Nat Butler (ASU), Diego Gonzalez (UNAM), Alexander Kutyrev (GSFC/UMD),
William H. Lee (UNAM), Margarita Pereyra (UNAM), and
Tanner Wolfram (ASU) report:

We observed the location of the Swift/UVOT transient (Breeveld et al.,
GCN Circ. 24296
Loading...
 
 ) with the Reionization and Transients Infrared Camera
(RATIR;
www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio
Astron��mico Nacional on Sierra San Pedro Martir from 2019/04 28.28 to
2019/04 28.49 UTC (approximately 3 d after the GW trigger), obtaining
a total of 1.92 hours exposure in the r and i bands and 1.21 hours
exposure in the Z, Y, J, and H bands.

For a source within the UVOT error circle, in comparison with the
USNO-B1 and 2MASS catalogs, we obtain the following upper limits (3-sigma):

  g > 23.5
  r > 23.4
  i > 23.3
  Z > 22.2
  Y > 22.2
  J > 21.8
  H > 21.4

The nearby objected reported by Palmese et al. (GCN Circ. 24312
Loading...
 
 ) is
detected in our images at H~20.1 mag.

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.

We thank the staff of the Observatorio Astronomico Nacional in San Pedro
Martir

N. R. Tanvir (U. Leicester), C. Gonzalez-Fernandez (IoA, U. Cambridge),
A. J. Levan (Radbound U.), D. B. Malesani (DAWN/NBI and DARK/NBI),
P. A. Evans (U. Leicester) report on behalf of the VINROUGE collaboration:

The location of the variable source reported in Swift/UVOT
observations (Breeveld et al., GCN 24296
Loading...
 
 ) appears in a field
imaged by the 4m VISTA telescope as part of our follow-up of the
binary neutron star merger S190425z (LVC collaboration, GCN 24168
Loading...
 
 ).
The observations were obtained on 2019-04-28 07:55 UT in the 2.15 um
Ks-filter.  We find no significant flux at the transient location,
corresponding to a 2-sigma limiting magnitude of K(AB)~20.6.
The absence of a detection in these observations suggests that
either it has rapidly faded and/or is not very red in UV-nIR colours.

The faint constant source, close to the UVOT position, noted by 
Palmese et al. (GCN 24312
Loading...
 
 ), is marginally visible in our imaging,
at about the 2-sigma level.

K. Morihana (Nagoya U.), M. Jian (U. of Tokyo), T. Nagayama (Kagoshima
U.) on behalf of J-GEM collaboration

We carried out NIR photometric follow-up observation of Swift/UVOT
transient (Breeveld et al.,GCN 24296) of the GW event S190425z (GCN
24168
Loading...
 
 ) with the near-infrared (J, H, Ks) simultaneous imaging camera
SIRIUS attached to the IRSF (InfraRed Survey Facility) 1.4 m telescope
in Sutherland Observatory, South Africa.

The observation started on 2019-04-28 00:44:28 UT. The exposure time
on the source is 40 min. A very faint source (possibly noise) is seen
at the position of Swift/UVOT transient in the J-band image. The
simple aperture photometry returns J=20.2 mag (Vega system), but it is
quite unsure. The conservative upper limit magnitudes for the
JHKs-band images are 18.8 mag, 18.4 mag, and 16.9 mag (Vega system),
respectively.

V. Lipunov, N.Tyurina, E. Gorbovskoy, V.Kornilov, D.Vlasenko, 
V.Vladimirov, D.Zimnukhov, A.Kuznetsov, P.Balanutsa, I.Gorbunov, A. 
Chasovnikov,  V.Grinshpun, F.Balakin, A.Chasovnikov 
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C. Lopez, C.Francile, F. Podesta (Observatorio Astronomico  Felix 
Aguilar OAFA, San Juan National University),

H.Levato (Instituto de Ciencias Astronomicas, de la Tierra y del Espacio 
ICATE,SJNU)

R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres (The Instituto 
de Astrofisica de Canarias),

D. Buckley (South African Astronomical Observatory),

O. Gress, N.M. Budnev, O.Ershova (Applied Physics Institute, Irkutsk State 
University),

V. Yurkov, A. Gabovich, Yu. Sergienko, D. Kobcev (Blagoveschensk EducationState 
University),

A. Tlatov, V.Senik, A.V. Parhomenko, D. Dormidontov (Kislovodsk Solar  Station 
of the Pulkovo Observatory),

Global MASTER-Net (http://observ.pereplet.ru, Lipunov et al., 2010, 
Advances in Astronomy, vol. 2010, 30L)   started inspect of the 
LIGO/Virgo S190425z errorbox (Singer et al. GCN 24168
Loading...
 
 ) 3133 sec after 
trigger time at 2019-04-25  09:10:18 UT  (Lipunov et al. GCN 24167
Loading...
 
 ).


MASTER-IAC observed Swift OT (Breeveld et al., GCN 24296
Loading...
 
 )  at 2019-04-26 
01:45:59 with mlim=20.0, and  at  2019-04-26 01:57:23 with mlim=20.0
during automatic inspect of GW190425.

There is optical transient with m_OT ~ 19.0  detected at both 
images.

MASTER-OAFA observed these coordinates at 2019-04-26 05:24:35 during 
automatic GW190425 inspection with unfiltered  mlim=19.0. There is no OT 
detection.

MASTER-SAAO  observed this area at 2019-04-27 21:15:24  and at 2019-04-27 
21:26:02 with mlim=21.0 and at  2019-04-26 04:01:55  with mlim=19.3 during 
automatic GW190425 inspection . There is no OT detection.
All instrumental unfiltered magnitude is W = 0.2B + 0.8R with respect to 
USNO B reference stars.

The object detected by Swift possibly connected with the blue flare on 
fast moving cool AllWISE star (RA,DEC) = 255.5777822 -12.4869992 (2" per 
yr!).

So this OT not connected with Gravitational Waves Event.
You can find below the community observations of the Swift OT 
region:

Telescope   Apr      Limit    OT   Filt    GCN

Zwicky      25.4      20.5    -    R      24302
Zwicky      25.4      20.5    -    g      24302
ASAS-SN     25.4      18.7    -    g      24313
Gattini     25.5      15.2    -    J      24306
Zwicky      25.5      20.5    -    R      24302
KMTNet SSO  25.6      21.5    -    R      24318
MASTER-IAC  26.1      20.0   19.0  W      This
MASTER-OAFA 26.2      19.0   19.0  W      This
Zwicky      26.3      20.5    -    g      24302
Gattini     26.4      15.2    -    J      24306
Zwicky      26.5      20.4    -    R      24302
ASAS-SN     26.5      18.7    -    g      24313
Swift       26.8       ?     17.7  U      24296
ASAS-SN     27.3      18.4    -    g      24313
MASTER-SAAO 27.88     21.0    -    W      This
LCO SAAO    27.9      21.5    -    R      24307
Lulin       28.8      21.5    -    R      24301

These data do not contradict the hypothesis of a short (10-15 minutes 
flash) on a red-brown dwarf.
The message may be cited.

Seo-Won Chang (ANU/OzGrav), Christian Wolf (ANU/OzGrav), Christopher A. Onken (ANU), Lance Luvaul (ANU), Susan Scott (ANU/OzGrav) report on behalf of the SkyMapper Transient survey collaboration:


We checked the SkyMapper observations at the location of the Swift UVOT candidate (Breeveld et al. GCN 24296
Loading...
 
 ). These images were taken with the 1.35-m ANU SkyMapper telescope at Siding Spring Observatory about 6 hours after the GW detection in response to LIGO/Virgo GW trigger S190425z (LVC collaboration, GCN 24168
Loading...
 
 ).  We do not see any transient down to an i-band (779/140 nm) magnitude of 20 (AB mag) at the two epochs: 2019-04-25 14:17:00 and 2019-04-25 14:25:53 UT. Our magnitude limits were obtained by calibrating with the zero-point from the SkyMapper Data Release 2 (Onken et al. 2019).

Y.-D. Hu, A. J. Castro-Tirado, X.-Y. Li, A. Ayala, E. Fernandez-Garcia
and F. J. Aceituno (IAA-CSIC), R. Sanchez-Ramirez (INAF-IAPS), M. D.
Caballero-Garcia (ASU-CAS) and N. Castro-Rodriguez (GRANTECAN, IAC,
ULL), on behalf of a larger collaboration, report:

Following the detection of Swift/UVOT of a transient (Breeveld et al.,
GCN 24296
Loading...
 
 ) within the error area of the GW event S190425z (LIGO
Scientific Collaboration and the Virgo Collaboration, GCN  24168
Loading...
 
 ), we
observed the target with the 1.5m telescope at the  Observatorio de
Sierra Nevada (Spain) in the R-band, starting on Apr  27, 03:44 UT. The
co-add of 3 frames (600s each) revealed no object down to 22.3 mag at
the position of the UVOT source. Deeper images were taken at the 10.4m
GTC telescope equipped with OSIRIS in La Palma (Spain) starting on Apr
27, 05:11 UT. The potential host galaxy reported by Palmese et al., GCN
24312
Loading...
 
 ) is detected in our 60s frames with r = 22.8+-0.2.


We acknowledge the excellent support from the GTC staff.

M. Nicholl (Edinburgh), R. Cartier (CTIO), I. Pelisoli (Potsdam), E. Berger, P. Blanchard, T. Eftekhari, S. Gomez, G. Hosseinzadeh, A. Villar, P. Williams (Harvard), P. Cowperthwaite (Carnegie), K. Alexander, D. Coppejans, W. Fong, R. Margutti, G. Terreran (Northwestern), R. Chornock (Ohio), J. Braga (INPE), L. Chomiuk, J. Strader (MSU), C. Clemens, D. Reichart (UNC), M. Drout (Toronto), D. Sand, N. Smith (Arizona), D. Kasen (Berkeley), B. Metzger (Columbia)

We report spectroscopic observations with the 4m SOAR telescope and Goodman spectrograph, of two potential electromagnetic counterparts to the gravitational wave trigger S190425z (GCN 24168
Loading...
 
 ): ZTF19aasckkq and ZTF19aasckwd, reported by ZTF/GROWTH (Anand et al, GCN 24311
Loading...
 
 ). 

These candidates were deemed to be the most likely counterparts as they are offset from bright galaxies and have low spectroscopic or photometric redshifts. ZTF19aasckkq has been detected in follow-up photometry by Perley et al. (GCN 24314
Loading...
 
 ), Malesani et al. (GCN 24319
Loading...
 
 ) and Ahumada et al. (GCN 24320
Loading...
 
 ).

SOAR classifications:

ZTF19aasckwd is a young Type Ia SN at z~0.15, consistent with the photometric redshift of the nearby galaxy.

ZTF19aasckkq also shows clear SN features in the spectrum. Using the code SNID (Blondin & Tonry, 2007) we find good matches to Type IIb SNe at z~0.05, consistent with the galaxy redshift.

Tomas Ahumada (UMD), Michael W. Coughlin (Caltech), Kai Staats
(Northwestern), Kevin Burdge (Caltech), Richard G. Dekany
<https://arxiv.org/search/astro-ph?searchtype=author&query=Dekany%2C+R+G>
(Caltech), Dmitry A. Duev
<https://arxiv.org/search/astro-ph?searchtype=author&query=Duev%2C+D+A>
(Caltech), Michael Feeney
<https://arxiv.org/search/astro-ph?searchtype=author&query=Feeney%2C+M>
(Caltech), S. R. Kulkarni
<https://arxiv.org/search/astro-ph?searchtype=author&query=Kulkarni%2C+S+R>
(Caltech), Reed Riddle
<https://arxiv.org/search/astro-ph?searchtype=author&query=Riddle%2C+R>
(Caltech) on behalf of the KPED team and the Global Relay of Observatories
Watching Transients Happen (GROWTH) collaboration.

We used the Kitt Peak EMCCD Demonstrator (KPED) on the Kitt Peak 84-inch
telescope (Coughlin et al 2019b) to obtain 300 s r-band images for ZTF
optical transients listed in Kasliwal et al. (GCN 24191
Loading...
 
 ) and Anand et al.
(GCN 24311
Loading...
 
 ) starting at 9:13:24 UT on 2019-04-27.

The measurement of ZTF19aasckkq is consistent with Perley et al. (GCN
24314
Loading...
 
 ) and we report upper limits for the rest of the transients.
Magnitudes are derived after calibrating against PS1:

  ID                            JD RA         DEC magnitude

ZTF19aasckkq    2458600.9291 248.413102  13.910183 r = 20.29 +- 0.18

ZTF19aaskbzh    2458600.9541 206.393046  69.329244 r > 19.65 +- 0.03

ZTF19aasejil       2458600.9837 261.945810    1.653720 r > 20.38 +- 0.34

ZTF19aasckkm   2458600.9248 247.302345  12.930679 r > 19.79 +-  0.18

More observations for this objects are scheduled.


The KPED team thanks the National Science Foundation, the National Optical
Astronomical Observatory and the Murty family for support in the building
and operation of KPED.

L. Izzo (HETH/IAA-CSIC), D. B. Malesani (DAWN/NBI and DARK/NBI), R. 
Carini (INAF/OAR) report:

We observed the field of ZTF19aasckkq, reported by the Zwicky Transient 
Facility (Anand et al., GCN 24311
Loading...
 
 ) to lie within the localization area 
of the LIGO/Virgo trigger S190425z (GCN 24168
Loading...
 
 ). We used the Nordic 
Optical Telescope (NOT) located in La Palma (Canary Islands, Spain) and 
equipped with the AlFOSC camera.

We report the following magnitudes on the approximate date April 28.14 
UT (2.8 days after the explosion of S190425z):

g = 20.63 +- 0.02
r = 20.33 +- 0.02
i = 20.29 +- 0.02

These magnitudes are calibrated against the Pan-STARRS survey; no 
subtraction of the host galaxy was attempted, but the target is 
relatively isolated and host contamination should not be a major 
contribution. Our measurements are consistent with those reported by 
Anand et al. (GCN 24311
Loading...
 
 ) on April 26 (unspecified time), as well as by 
Perley et al. (GCN 24314
Loading...
 
 ) on April 27.14 UT.

The object seems therefore slowly variable, and less likely to be 
associated with S190425z.

Myungshin Im (SNU), Joonho Kim (SNU), Gregory S. H. Paek (SNU),  Chung-Uk
Lee (KASI), Seung-Lee Kim (KASI), Hyung Mok Lee (KASI), on behalf of a
larger collaboration

 We checked the KMTNet image at the location of the UVOT transient
(Breeveld et al., GCN Circ. 24296
Loading...
 
 ). The image was taken at 2019-04-25
14:05:29 (UT) at the KMTNet Siding Spring Observatory station, about 6
hours after the GW detection (LVC collaboration, GCN Circ. 24168
Loading...
 
 ) and 28
hours before the reported UVOT detection. We do not find any transient at
the UVOT location down to the preliminary magnitude limit of R<21.5
(3-sigma, point source). We do find the reported faint host galaxy
candidate in our KMTNet data (Palmese et al., GCN Circ. 24312
Loading...
 
 )

 We thank the KMTNet operators for performing the observation.

L.P. Xin (NAOC), X.H. Han (NAOC), J.Y. Wei (NAOC), C. Wu (NAOC), 
D. Turpin (NAOC), J.G. Ducoin (CNRS/LAL), D. Corre (CNRS/LAL), 
L. Huang (NAOC), Y. Xu (NAOC), H.B. Cai (NAOC), J. Wang (NAOC), 
X.M. Lu (NAOC), Y.L. Qiu (NAOC), J.S. Deng (NAOC), L. Jia (NAOC), 
S.C. Zou (NAOC), S.F. Liu (NAOC), Q.C. Feng (NAOC), H.L. Li (NAOC), 
D.W. Xu (NAOC), Y.J. Xiao (NAOC), W.L. Dong (NAOC), Y.T. Zheng (NAOC), 
P. P. Zhang (NAOC), R.S. Zhang (NAOC), E.W. Liang (GXU), 
X.G. Wang (GXU),  Z.G. Dai (NJU), X.Y. Wang (NJU), Y.G. Yang (HBNU), 
J.R. Mao (YNAO),  B. Cordier (CEA/AIM), S. Basa (CNRS/LAM), 
J.L. Atteia (UPS/IRAP),  D. Götz (CEA/AIM),  A. Claret (CEA/AIM), 
N. Leroy (CNRS/LAL), C. Lachaud (CNRS/APC), S. Antier (CNRS/APC/CNES), 
S.N. Zhang (IHEP), B.B. Wu (IHEP),  report on behalf of the SVOM Ground Follow-up Group:

We observed the LIGO/Virgo trigger S190425z with GWAC-F60A.
Two 60cm GWAC-F60(A/B) are operated by Guangxi University and NAOC,
CAS, at Xinglong Observatory. China. They are equipped with Standard
Johnson filters and 2Kx2K Andor CCD (FOV~18x18 arcmin). GWAC-F60(A/B)
are used for galaxy-targeted observations. The galaxies are selected
from the GLADE catalog (Version 2.3, Dalya et al. 2018) in the probability
skymap of GW event. All these galaxies were observed in clear band. 
The weather was not good during the  observations.

The first image was taken ~6 hours after the event trigger. No credible
new source was detected in our pipeline. A total number of
80 galaxies were observed. The coordinates (J2000) of galaxies,
the observation time, the limit magnitude (3sigma) and telescopes 
are listed below:

 # Ra	     Dec            start-obs(UTC)   Limit (R)     Telescope
246.40900  16.45500   2019-04-25T14:07:30.157  16.86  F60A
235.47600  28.13410   2019-04-25T12:26:20.678  20.16  F60A
236.94100  28.64190   2019-04-25T13:38:20.485  18.81  F60A
186.25200  28.55850   2019-04-25T12:14:11.215  20.25  F60A
241.23600  23.93290   2019-04-25T13:09:22.662  16.66  F60A
243.74100  21.93830   2019-04-25T13:49:55.528  14.15  F60A
246.11400  19.48260   2019-04-25T13:44:10.488  16.35  F60A
247.40100  15.65840   2019-04-25T14:03:29.676  17.11  F60A
252.98900  4.38356    2019-04-26T15:14:39.330  20.03  F60A
253.53600  -7.63537   2019-04-26T15:41:09.103  19.00  F60A
248.25700  22.79720   2019-04-26T16:18:33.855  18.88  F60A
246.40900  16.45500   2019-04-26T13:39:32.350  19.24  F60A
242.31500  25.71250   2019-04-26T13:29:26.576  18.96  F60A
101.82200  33.56730   2019-04-26T13:03:41.172  18.12  F60A
213.21400  35.71070   2019-04-26T19:31:21.044  15.55  F60A
252.26500  -17.64590  2019-04-26T18:17:23.676  15.12  F60A
213.61300  36.40440   2019-04-26T19:12:15.038  16.48  F60A
252.69500  4.60474    2019-04-26T15:10:41.648  18.50  F60A
253.24500  2.40099    2019-04-26T15:06:31.427  18.98  F60A
252.92700  -2.61525   2019-04-26T15:30:55.776  18.12  F60A
251.59400  9.03763    2019-04-26T14:23:38.733  17.37  F60A
188.92200  26.52300   2019-04-26T12:50:39.801  19.69  F60A
236.90100  26.06370   2019-04-26T12:40:17.254  19.40  F60A
252.71300  8.78387    2019-04-26T15:57:48.620  18.05  F60A
216.14600  35.27980   2019-04-26T13:12:20.095  18.89  F60A
256.23700  -1.53050   2019-04-26T19:27:31.002  14.74  F60A
239.01600  24.44800   2019-04-26T18:58:18.867  16.39  F60A
240.75100  27.01030   2019-04-26T12:36:02.920  18.67  F60A
246.06300  20.18360   2019-04-26T14:06:52.457  18.67  F60A
256.68100  -4.93311   2019-04-26T19:42:41.710  14.82  F60A
236.97500  25.72940   2019-04-26T16:10:06.932  18.87  F60A
189.55500  28.93690   2019-04-26T12:03:09.117  18.55  F60A
203.60500  34.69040   2019-04-26T12:59:12.069  19.63  F60A
240.68800  25.25220   2019-04-26T14:45:39.591  19.17  F60A
251.85200  -20.14170  2019-04-26T18:25:26.961  13.73  F60A
252.33700  -17.64450  2019-04-26T16:46:18.132  14.91  F60A
254.52400  -21.27410  2019-04-26T18:29:34.531  13.66  F60A
265.63300  0.21675    2019-04-26T18:54:30.920  13.77  F60A
252.72300  -15.00400  2019-04-26T16:22:46.980  16.61  F60A
217.50600  36.36090   2019-04-26T19:08:30.994  16.65  F60A
242.40600  28.05180   2019-04-26T14:31:48.522  19.80  F60A
258.11900  -9.12416   2019-04-26T16:26:50.153  16.71  F60A
218.40500  35.96650   2019-04-26T14:11:05.568  19.82  F60A
200.21300  43.96540   2019-04-26T12:26:20.960  19.19  F60A
243.14800  29.48450   2019-04-26T19:16:03.251  16.82  F60A
208.41000  36.13420   2019-04-26T13:33:42.807  19.49  F60A
249.86000  11.21050   2019-04-26T14:27:45.663  19.03  F60A
216.08600  36.46140   2019-04-26T12:16:57.909  19.57  F60A
190.43600  35.06290   2019-04-26T13:08:04.914  19.41  F60A
212.69800  35.91340   2019-04-26T12:08:27.646  19.09  F60A
243.14800  29.48480   2019-04-26T18:42:22.185  16.77  F60A
251.94600  -7.21269   2019-04-26T16:30:59.956  16.95  F60A
203.64600  34.77790   2019-04-26T19:19:52.570  15.29  F60A
253.27000  -16.29090  2019-04-26T18:13:21.035  15.42  F60A
221.59100  32.78010   2019-04-26T13:20:54.590  20.53  F60A
182.57600  26.43080   2019-04-26T14:19:29.899  20.04  F60A
243.14700  29.36490   2019-04-26T19:35:09.298  15.77  F60A
252.07700  6.31221    2019-04-26T14:53:56.092  18.74  F60A
254.78000  -5.74199   2019-04-26T15:45:20.977  17.63  F60A
253.60000  -9.88924   2019-04-26T16:01:51.545  16.91  F60A
193.51000  29.60370   2019-04-26T13:25:15.579  19.72  F60A
194.91500  53.34130   2019-04-26T12:12:42.478  20.34  F60A
242.27700  24.87030   2019-04-26T18:46:29.445  15.58  F60A
260.77200  12.69540   2019-04-26T16:05:56.399  17.81  F60A
256.25200  -1.54133   2019-04-26T19:38:57.637  14.77  F60A
253.72400  -16.95200  2019-04-26T16:50:26.458  14.38  F60A
205.41500  55.67070   2019-04-26T16:14:20.651  19.45  F60A
252.09000  6.22276    2019-04-26T14:49:46.057  18.45  F60A
196.48300  53.65920   2019-04-26T16:35:23.719  18.93  F60A
240.66900  37.35940   2019-04-26T12:21:33.662  19.43  F60A
252.38800  6.01625    2019-04-26T14:57:55.285  18.43  F60A
253.03200  -17.05380  2019-04-26T18:21:23.262  14.86  F60A
254.50500  -1.82269   2019-04-26T15:26:51.357  17.91  F60A
240.36900  22.42770   2019-04-26T14:15:09.801  19.36  F60A
232.92900  40.86490   2019-04-26T13:16:36.533  20.10  F60A
243.89800  19.45340   2019-04-26T18:50:43.803  15.42  F60A
255.21800  2.10185    2019-04-26T15:18:42.705  18.77  F60A
197.38900  53.49420   2019-04-26T12:31:38.012  20.40  F60A
250.01400  15.88340   2019-04-26T14:02:46.419  19.04  F60A
245.79700  16.93260   2019-04-26T13:58:39.077  19.32  F60A


This circular is citable.

D. A. Perley, C. M. Copperwheat, and K. L. Taggart (LJMU) report on 
behalf of the Global Relay of Observatories Watching Transients Happen 
(GROWTH) collaboration:

We acquired a series of 60-second exposures of ZTF19aasckkq (Anand et 
al., GCN 24311
Loading...
 
 ), an optical transient in the error region of LIGO/Virgo 
S190425z (GCN 24168
Loading...
 
 ), using the IO:O imager on the 2m Liverpool 
Telescope in the u, g, r, i, and z filters between 03:17:56 and 03:30:00 
UT on 2019-04-27.

The transient is detected with the following magnitudes (measured after 
image subtraction and calibrated relative to PS1):

JD          	magnitude
2458600.6384	g = 20.66 +/- 0.18
2458600.6395	r = 20.37 +/- 0.17
2458600.6406	i = 20.28 +/- 0.23
2458600.6416	z = 20.09 +/- 0.38

It is not detected in u-band.  These suggest a moderately but not 
extremely red transient and show no obvious evolution relative to the 
ZTF imaging on 2019-04-26 (g = 20.86 +/- 0.18).













DisclaimerNone

B. J. Shappee (IfA-Hawaii), C. S. Kochanek (OSU), K. Z. Stanek (OSU), S.
Holmbo (Aarhus), A. Franckowiak (DESY), T. W.-S. Holoien (Carnegie
Observatories), J. L. Prieto (Diego Portales; MAS), Subo Dong (KIAA-PKU),
 T. A. Thompson (OSU), J. F. Beacom (OSU)


Swift reported a possible counterpart (Breeveld et al., GCN #24296
Loading...
 
 ) to
LIGO/Virgo
Alert GCN #24168
Loading...
 
  of a BNS merger.  The reported detection was acquired
on 2019-04-26.784282
UT Swift UVOT u=17.74 +/- 0.18 mag (Vega). ZTF (Andreoni et al., GCN #24302
Loading...
 
 
) reported non-detections 9 hours before the reported Swift observations.


ASAS-SN observations cover both 7 hours before and 12 hours after the
reported Swift transient with 3-sigma g-band limits deeper than the
reported u-band detection:

2019-04-25.4180376   >18.755

2019-04-26.4875420   >18.749

2019-04-27.3040667   >18.421



The transient Swift observed must have evolved on a short timescale or have
been very blue (u-g)~-1.



We would like to thank Las Cumbres Observatory and its staff for their
continued support of ASAS-SN. ASAS-SN is funded in part by the Gordon and
Betty Moore Foundation through grant GBMF5490 to the Ohio State University,
NSF grant AST-1515927, the Mt. Cuba Astronomical Foundation, the Center for
Cosmology and AstroParticle Physics (CCAPP) at OSU, the Chinese Academy of
Sciences South America Center for Astronomy (CASSACA), and the Villum
Fonden (Denmark). For more information about the ASAS-SN project, see
http://www.astronomy.ohio-state.edu/asassn/index.shtml.

A. Palmese (Fermilab), M. Soares-Santos (Brandeis U.), L. Santana-Silva (OV/UFRJ), A. Drlica-Wagner (Fermilab), K. Herner (Fermilab), R. Morgan (U Wisconsin-Madison)

We searched for previous observations at the position of the UVOT candidate (Breeveld et al. GCN Circ. 24296
Loading...
 
 ) in archival DECam data which we have compiled and processed as part of the Blanco Images of the Southern Sky (BLISS) project (PIs: Soares-Santos, Drlica-Wagner). The candidate was identified as part of the counterpart search for the LVC event S190425z (LIGO/VIRGO Collaboration GCN (Circ. 24168).

We find a faint object <1 arcsec away from the UVOT candidate. Visual inspection suggests it is a galaxy. Its AB magnitude is  r=22.95+-0.096 (MAG_AUTO) at position (J2000):
RA 255.57996 deg
Dec -12.48536 deg
We suggest to observe this object in other bands or spectroscopically to assess its origin and redshift.

Shreya Anand (Caltech), Mansi M. Kasliwal (Caltech), Michael W. Coughlin (Caltech), Tomas Ahumada (UMD), Daniel A. Perley (LJMU), Varun Bhalerao (IITB), Danny Goldstein (Caltech), �Leo P. Singer (NASA GSFC), Igor Andreoni (Caltech), Dmitry Duev (Caltech), S. Bradley Cenko (NASA GSFC), Eric C. Bellm (UW), Kishalay De (Caltech), Anna Ho (Caltech), Harsh Kumar (IITB), Gaurav Waratkar (IITB), Chris Copperwheat (LJMU), Virginia Cunningham (UMD), Shaon Ghosh (UWM), Ariel Goobar (OKC), David Kaplan (UWM), Jesper Sollerman (OKC), Joshua S. Bloom (UCB), M. Bulla (OKC), Nobuyuki Kawai (Tokyo Tech), Yoichi Yatsu (Tokyo Tech), Katsuhiro Murata (Tokyo Tech), Hidekazu Hanayama (IAO), Takashi Horiuchi (IAO), G. C. Anupama (IIA), G. Helou (IPAC)

On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations

We continued observations of the gravitational wave trigger S190425z (LVC et al. GCN 24168
Loading...
 
 ) with ZTF on UT 2019-04-26. We covered a total of 4950 sq deg in g-band and r-band with over 50% of the enclosed probability targeted based on the original sky map and 24% actual probability enclosed based on the new sky map. Each exposure on the second night was 90s, with a typical depth of 21 mag. See details in Kasliwal et al. GCN 24191
Loading...
 
  for additional details on data processing.

Objects with a spectroscopic host galaxy redshift higher than 0.1 were excluded and photometric redshifts, where available are noted below. Additional candidates with no detections prior to merger, inside the 90% localization area of the LALInference sky map are:

------------------------------------------------------------------------------------------------------------------

ZTF Name | RA (deg) | DEC (deg) ��| Filter | Mag ��| Magerr �| Notes

------------------------------------------------------------------------------------------------------------------

ZTF19aasckwd | 253.1643781 | �10.6022943 | r | 20.15 | 0.13 |

ZTF19aasfogv | 261.8430161 | -11.3338523 | g � | 20.53 | 0.18 | [hostless] [lowb]

ZTF19aasejil | 261.9458106 | ��1.6537207 | g | 20.53 | 0.14 | z~0.199 +/- 0.035 [nuc]

ZTF19aaryxjf | 254.5952784 | �-3.9847379 | g | 19.95 | 0.08 | z~0.083 +/- 0.015 [nuc]

ZTF19aascxux | 258.2933102 | �17.2938689 | g | 20.56 | 0.13 �

ZTF19aasdajo | 254.3550291 | �11.9961079 | g | 20.70 | 0.20 | z~0.292 +/- 0.067

ZTF19aasbamy | 231.2656676 | �24.9275799 | g | 20.66 | 0.15 | z~0.201 +/- 0.047

ZTF19aasckkq | 248.4131017 | �13.9101828 | g | 20.86 | 0.18 | z=0.0528 [specz]

ZTF19aarycuy | 244.0832042 | �21.7409392 | r | 20.07 | 0.15 | z~0.127 +/- 0.011 [nuc]

ZTF19aasbphu | 245.5831354 | �21.4081853 | r | 19.71 | 0.13 | z~0.0971 +/- 0.0292

�ZTF19aasbaui | 235.2496342 | �24.0816102 | g | 20.49 | 0.14 | z~0.216 +/- 0.052

�ZTF19aarxxwb | 288.6933231 | �-3.0075058 | g | 18.89 | 0.07 | [hostless] [lowb]

�ZTF19aashlts | 253.1875476 | -19.0941338 | r � | 19.95 | 0.11 | [lowb]

------------------------------------------------------------------------------------------------------------------

Notes:

[specz] : Spectroscopic redshift.

[hostless] : No discernable host galaxy.

[nuc] : Close to the host nucleus

[lowb] : Galactic latitude less than 20 degrees

Our most promising event is ZTF19aasckkq as it is -16.3 absolute mag  and we encourage follow-up. We also encourage due diligence follow-up of ZTF19aasckwd and ZTF19aascxux. We caution these targets are somewhat fainter and our upper limits relatively less constraining on age. We also caution that we cannot rule out the supernova hypothesis.

Additional follow-up and analysis is ongoing.

ZTF and GROWTH are worldwide collaborations comprising Caltech, USA; IPAC, USA, WIS, Israel; OKC, Sweden; JSI/UMd, USA; U Washington, USA; DESY, Germany; MOST, Taiwan; UW Milwaukee, USA; LANL USA; Tokyo Tech, Japan; IIT-B, India; IIA, India; LJMU, UK; TTU USA and USyd, Australia. ZTF acknowledges the generous support of the NSF under AST MSIP Grant No 1440341. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert filtering and follow-up co-ordination is being undertaken by the GROWTH marshal system (Kasliwal et al. 2019).

B. J. Shappee (IfA-Hawaii), C. S. Kochanek (OSU), K. Z. Stanek (OSU),
S. Holmbo (Aarhus), A. Franckowiak (DESY), T. W.-S. Holoien (Carnegie
Observatories),
J. L. Prieto (Diego Portales; MAS), Subo Dong (KIAA-PKU),  T. A. Thompson
(OSU), J. F. Beacom (OSU)

ASAS-SN covered 10% of the probability region in the 1 hour preceding the
LIGO/Virgo Alert GCN #24168
Loading...
 
  of a BNS merger through normal operations.
Following, the LIGO/VIRGO alert optical follow-up was triggered with the
All-Sky Automated Survey for SuperNovae (ASAS-SN, Shappee et al. 2014;
Kochanek et al. 2017).   ASAS-SN covered 67% of the probability region in
the 24 hours after the LIGO/VIRGO alert through a combination of normal
operations and triggered observations.  The majority of the remaining
probability region was Sun constrained.  We obtained 6 epochs on the
highest probability regions during that time. Candidates were scanned in
near real time. No obvious candidates were discovered. Given the lunation,
our depth was typically between g~18-18.5 mag.

Our coverage is shown here:
http://www.astronomy.ohio-state.edu/~assassin/LIGO/S190425z_coverage.png

We would like to thank Las Cumbres Observatory and its staff for their
continued support of ASAS-SN. ASAS-SN is funded in part by the Gordon and
Betty Moore Foundation through grant GBMF5490 to the Ohio State University,
NSF grant AST-1515927, the Mt. Cuba Astronomical Foundation, the Center for
Cosmology and AstroParticle Physics (CCAPP) at OSU, the Chinese Academy of
Sciences South America Center for Astronomy (CASSACA), and the Villum
Fonden (Denmark). For more information about the ASAS-SN project, see
http://www.astronomy.ohio-state.edu/asassn/index.shtml

Iair Arcavi (Tel Aviv University), D. Andrew Howell (LCO/UCSB), Curtis
McCully (LCO), Daichi Hiramatsu (LCO/UCSB), Jamison Burke (LCO/UCSB), Craig
Pellegrino (LCO/UCSB) on behalf of the Las Cumbres GW Follow-up
Collaboration


We observed the field of the UVOT transient (Breeveld et al. GCN 24296
Loading...
 
 )
with a Las Cumbres Observatory 1m telescope at the South African
Astronomical Observatory in the g and r bands starting at 2019-04-27 21:40
UT. We do not see the transient down to a g-band limiting magnitude of
roughly 21.8, and an r-band limiting magnitude of 21.5 (determined by
comparison to PS1 images).

K. De (Caltech), M. Hankins (Caltech), S. M. Adams (Caltech), M. M.
Kasliwal (Caltech), M. Coughlin (Caltech), I. Andreoni (Caltech), S.
Anand (Caltech), L. Singer (NASA GSFC), T. Ahumada (UMD),  A. Moore
(ANU), J. Soon (ANU), M. Ashley (UNSW), T. Travouillon (ANU)

report on behalf of the Palomar Gattini-IR team and the larger GROWTH
(Global Relay of Observatories Watching Transients Happen)
collaboration

The Palomar Gattini-IR survey (Moore and Kasliwal 2019) observed the
location of the Swift UVOT counterpart candidate (GCN #24296
Loading...
 
 ) for the
BNS gravitational wave event S190425z (GCN #24168
Loading...
 
 ) on UT 2019-04-26
09:59 and UT 2019-04-25 at 10:54. Forced photometry on the images show
no source at the reported location down to a limiting magnitude of
15.2 AB mag in J band. The non-detections rule out bright infrared
emission from the source prior to the Swift detection.

Aaron Tohuvavohu (PSU), Phil Evans (U. Leicester), Mike Siegel (PSU),
Frank Marshall (NASA GSFC), Brad Cenko (NASA GSFC) and Jamie Kennea
(PSU) report on behalf of the Swift Gravitational Wave Galaxy Survey
(SGWGS) team

The position of the potential Swift/UVOT counterpart (Breeveld et
al. GCN. 24296) to the LIGO/Virgo S190425z trigger (LIGO/Virgo
Collaboration GCN. 24168)  was imaged by the Neil Gehrels Swift
Observatory on 2018, October 21/22 UT with the Swift
Ultraviolet/Optical Telescope in the u and uvw1 filters for a total
1.2 ks of exposure as part of the Swift Gravitational Wave Galaxy
Survey (PI Tohuvavohu). Examining the image we do not detect any
source at the position of the counterpart candidate to a 5-sigma
limiting magnitude of ~21 mag in U-band, corresponding to  ~ -14 mag
at the distance of the associated host galaxies (~100 Mpc).  These
magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the event.

The Swift Gravitational Wave Galaxy Survey is a 5 Million second
pre-imaging survey of the ~14,000 most likely host galaxies for BNS
mergers within ~100 Mpc. It is performed in the  u and uvw1 bands and
with XRT in the Photon Counting mode. It is currently ~43%
complete. When complete it will cover 41.2% of the integrated B-band
luminosity within 100 Mpc down to ~21 mag in u and uvw1 and
~5 �� 10 ���13 erg cm ���2 s ���1 in the X-rays (0.3 - 10 keV).

G. Waratkar, H. Kumar, V. Bhalerao (IITB), J. Stanzin, G. C. Anupama (IIA) report on behalf of the Global Relay of Observatories Watching Transients Happen (GROWTH) collaboration:

We imaged the location of the Swift/UVOT transient candidate (Breeveld et al., GCN 24296
Loading...
 
 ) for the counterpart of LIGO/Virgo S190425z with the 0.7m GROWTH-India telescope. We obtained a 600s g band image starting at UT 2019-04-27T20:07:44, and a 600s r band image starting at UT 2019-04-27T19:42:49. The source was not detected in either of the images, down to a limiting magnitude of 21.0.

The start time in the previous circular is incorrect and has been corrected
here.

LIGO/Virgo S190425z: Lulin observations of the Swift/UVOT transient

Albert Kong (NTHU), Han-Jie Tan (NCU), Po-Chieh Yu (NCU), Chow-Choong
Ngeow (NCU), Wing-Huen Ip (NCU)

On behalf of Global Relay of Observatories Watching Transients
Happen (GROWTH) collaborations

We used the 1m telescope at the Lulin Observatory in Taiwan to obtain
g- and r-band images of the transient found by Swift/UVOT (GCN 24296
Loading...
 
 ).
The observations started at 2019-04-27 19:30 UT and the exposure time is
300s for both filters. With a limiting magnitude of about 21.5 (AB) by
comparing to PS1 images, we do not detect the UVOT transient.

Igor Andreoni (Caltech), S. Bradley Cenko (NASA GSFC), F. Masci (IPAC), M. Graham (Caltech)

On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations

We report pre-detection forced photometry upper limits for the Swift/UVOT transient candidate (Breeveld et al., GCN 24296
Loading...
 
 ) from recent observations with the Zwicky Transient Facility (ZTF). Forced photometry was performed on images processed through the ZTF reduction and image subtraction pipelines at IPAC (Masci et al. 2019).

------------------------------------
date (UT) | filter | maglim
------------------------------------
2019-04-25T10:05:01.746 | r | 20.51
2019-04-25T10:07:12.096 | g | 20.48
2019-04-25T11:26:44.153 | r | 20.47
2019-04-26T07:49:33.277 | g | 21.58	
2019-04-26T09:36:47.686 | r | 20.42
------------------------------------

The candidate was detected with Swift/UVOT on 2019-04-26 at 18:49:22 UT (Breeveld et al., GCN 24296
Loading...
 
 ).  Thus, if associated with the gravitational wave event, the ZTF non-detections may constrain the rise time and temperature during the rise of the transient. 

The ZTF forced-photometry service was funded under the Heising-Simons Foundation grant #12540303 (PI: Graham). ZTF and GROWTH are worldwide collaborations comprising Caltech, USA; IPAC, USA, WIS, Israel; OKC, Sweden; JSI/UMd, USA; U Washington, USA; DESY, Germany; MOST, Taiwan; UW Milwaukee, USA; LANL USA; Tokyo Tech, Japan; IIT-B, India; IIA, India; LJMU, UK and USyd, Australia. ZTF acknowledges the generous support of the NSF under AST MSIP Grant No 1440341. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949.

Albert Kong (NTHU), Han-Jie Tan (NCU), Po-Chieh Yu (NCU), Chow-Choong Ngeow
(NCU), Wing-Huen Ip (NCU)

On behalf of Global Relay of Observatories Watching Transients Happen
(GROWTH) collaborations

We used the 1m telescope at the Lulin Observatory in Taiwan to obtain g-
and r-band images of the transient found by Swift/UVOT (GCN 24296
Loading...
 
 ). The
observations started at 2019-04-28 19:30 UT and the exposure time is 300s
for both filters. With a limiting magnitude of about 21.5 (AB) by comparing
to PS1 images, we do not detect the UVOT transient.

LIGO/Virgo S190425z: Transient found in Swift/UVOT counterpart search

A. A. Breeveld (MSSL-UCL), N. P. M. Kuin (UCL-MSSL), F. E. Marshall (NASA/GSFC),  P. Brown (TAMU),
S. R. Oates (Uni. of Warwick), M. H. Siegel (PSU), M. de Pasquale (Uni. of Istanbul),
S. D. Barthelmy (NASA/GSFC), A. Y. Lien (GSFC/UMBC), 
D. M. Palmer (LANL), T. Sakamoto (AGU), A. P. Beardmore (U. Leicester),
D. N. Burrows (PSU), S. Campana (INAF-OAB), S. B. Cenko (NASA/GSFC),
G. Cusumano (INAF-IASF PA), A. D'Ai (INAF-IASFPA), 
P. D'Avanzo (INAF-OAB), V. D'Elia(ASDC), S. Emery (UCL-MSSL), 
P. A. Evans (U. Leicester), P. Giommi (ASI), C. Gronwall (PSU), 
D. Hartmann (Clemson U.), J. A. Kennea (PSU), H. A. Krimm (NSF), 
A. Melandri (INAF-OAB), B. Mingo (U. Leicester), J. A. Nousek (PSU), 
P. T. O'Brien (U. Leicester), J. P. Osborne (U. Leicester), C. Pagani (U. Leicester), 
K. L. Page (U.Leicester), M. Perri (ASDC), 
J. L. Racusin (NASA/GSFC), B. Sbarufatti (INAF-OAB/PSU),
G. Tagliaferri (INAF-OAB), A. Tohuvavohu (PSU),
E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift team:

We report a candidate transient found in the UVOT search results of the
LVC event S190425z (LIGO/VIRGO Collaboration GCN Circ. 24168
Loading...
 
 ). 

On 2019-04-26 at 18:49:22 UT Swift UVOT took a 66.8 s exposure in the u band with 
exposure ID uu577997367I (target ID 07016575) which shows a new source when compared with
archived DSS images. The new source is not listed in the Gaia DR1, 2MASS or GSC2.3 
catalogs or Pan-STARRS and is not listed as a minor planet. 

The position is: 
RA = 255.5800 deg
Dec = -12.48562 deg
which is RA=17:02:19.2, Dec=-12:29:08.2 (J2000).

The magnitude using the UVOT photometric system  (Breeveld et al. 2011, AIP 
Conf. Proc. 1358, 373) is u=17.74 +/- 0.18 mag (Vega).

No source is found at this position in the XRT, with a 3-sigma upper limit of  
5.8 x 10^-2 ct s^-1, which corresponds to a 0.3-10 keV observed flux of 
2.5 x 10^-11 erg cm^-2 s^-1.

At this position, the distance estimate from the LALInference sky map has a mean 
of 132 Mpc with a sigma of 35 Mpc. 

There is a bright galaxy in the 2MPZ catalogue (Bilicki et al., 2014) 2MPZ
J17021587-1228210 at 68 arcsec (z = 0.022, D = 99 Mpc, abs K magnitude = 12.4),
which is 33 kpc away in projection. A second galaxy, 2MPZ J17020235-1229511 lies
250 arcsec away from the UVOT position. This galaxy has a distance of 106 Mpc in
the 2MPZ catalogue so the projected offset is 128 kpc. At the distance of these
galaxies, the absolute U magnitude would be -17.3, which is brighter than AT 2017gfo
Loading...
 
  at
t ~ 2 days.

This circular is an official product of the Swift team.

Curtis McCully (LCO), Daichi Hiramatsu (LCO/UCSB), D. Andrew Howell
(LCO/UCSB) Iair Arcavi (Tel Aviv University), Maria Drout (University of
Toronto), Jamison Burke (LCO/UCSB), Craig Peligrino (LCO/UCSB), Reinaldo de
Carvalho: (INPE), Francisco Fo��rster (Universidad de Chile), Ryan Foley
(UCSC), David Coulter (UCSC), Charles Kilpatrick (UCSC), David Sand (UA),
Stefano Valenti (UC Davis), Marcelle Soares-Santos (Brandeis), Sandro
Rembold (UFSM), Armin Rest (STSci), Daniel Kasen (UC Berkeley), Brian
Metzger (Columbia), Anthony Piro (Carnegie Obs.), Eliot Quataert (UC
Berkeley), Enrico Ramirez-Ruiz (UCSC), J. Craig Wheeler: (UT Austin), Franz
Bauer (Pontificia Universidad Catolica de Chile) Joshua Bloom (UC
Berkeley), Thomas Brink (UC Berkeley), Jeff Cooke (Swinburne University of
Technology), Alejandro Clocchiatti (Pontificia Universidad Catolica de
Chile), Alexei V. Filippenko (UC Berkeley), Wendy Freedman (University of
Chicago), Peter Garnavich (Notre Dame), Jorge Ernesto Horvath (Universidade
de Sao Paulo), Saurabh Jha (Rutgers), Robert Kirshner (Gordon and Betty
Moore Foundation), Kevin Krisciunas (Texas A&M), Huan Lin (FNAL), Barry
Madore (Carnegie Obs.),  Martin Makler (Centro Brasileiro de Pesquisas
Fi��sicas), Xavier Prochaska (UCSC), Adam Riess (STSci), Riccardo Sturani
(UFRN), Nicholas Suntzeff (Texas A&M), Masaomi Tanaka (Tohoku University),
Douglas Tucker (FNAL), Jozsef Vinko (Konkoly Observatory), Lifan Wang
(Texas A&M), Jonathan Brown (Ohio State University), Carlos Contreras
(STSci), Chris D'Andrea (UPenn), Georgios Dimitriadis (UCSC), David Jones
(UCSC), Michael Lundquist (UA), Gautham Narayan (STSci), Felipe Olivares
(Universidad de Chile), Antonella Palmese (FNAL), Yen-Chen Pan: (NAOJ),
Daniel Scolnic (University of Chicago), Weikang Zheng (UC Berkeley),
Antonio Bernardo (Universidade de Sao Paulo), Azalee Bostroem (UC Davis),
Ariadna Murguia Berthier (UCSC), O��smar Rodri��guez (Universidad Nacional
Andres Bello), Ce��sar Rojas-Bravo (UCSC), Matthew Siebert (UCSC), and
Iruata�� Souza (Centro Brasileiro de Pesquisas)

We report spectroscopic observations of PS19qp/AT 2019ebq
Loading...
 
 , the transient
reported by Pan-STARRS (Smith, et al., GCN 24210
Loading...
 
 ), using GMOS on Gemini
North at 2019-04-26 14:29:13. We combined 2x750s observations with a
central wavelength of 850nm.

We confirm the presence of broad P-cygni features identified by Morokuma et
al. (GCN 24230
Loading...
 
 )

as the calcium IR triplet. We find that the spectrum is consistent with a
reddened (Nicholl et al., 24217) type Ib/c supernova in agreement with
Carini et al. (GCN 24252
Loading...
 
 ) and Jencson et al. (GCN 24233
Loading...
 
 ).

We thank the Gemini staff for their rapid response making these
observations possible.

Bin Li, Hai-bin Zhao (PMO), Dong Xu, Zi-pei Zhu, Bang-yao Yu, Tian-meng 
Zhang, Xu Zhou, Chen-zhou Cui, Hui-juan Wang (NAOC), Xue-feng Wu, 
Zhi-ping Jin, Tian-rui Sun, Hao Lu, Ge-tu Zhaori, Ren-quan Hong, 
Long-fei Hu (PMO), Xiao-feng Wang, Wen-xiong Li (THU), Li-fan Wang 
(PMO/TAMU), Jin-zhong Liu (XAO), Ji-rong Mao, Jin-ming Bai (YNAO) report 
on behalf of the CNEOST collaboration:

We conducted optical imaging observations for gravitational wave alert 
with Chinese Near Earth Object Survey Telescope (CNEOST) at Xuyi 
astronomical station in Jiangsu Province, China (32.75N, 118.47E). The 
information of observations and preliminary results are listed below.

Alert: LIGO/Virgo S190425z (GCN 24168
Loading...
 
 )
StartTime (UT):               2019-04-26T11:49:02.152
EndTime (UT):                 2019-04-26T16:36:13.239
Skycover (Square Degree):     675.0
Telescope FoV (Square Degree): 9.0
#  id  CentRA(Degree)  CentDEC(Degree) LimiteMag3\sigma 5\sigma 10\sigma 
  Filter
       1    184.785507     26.824320      20.983      19.969      19.190 
      VR
       2    192.873947     29.601379      20.944      19.900      19.114 
      VR
       3    191.960449     32.390297      20.907      19.837      19.004 
      VR
       4    183.234314     29.591774      21.019      19.959      19.177 
      VR
       5    179.964020     21.201527      20.947      19.945      19.179 
      VR
       6    187.898514     26.821241      20.979      19.949      19.173 
      VR
       7    196.073746     29.603632      20.851      19.799      18.974 
      VR
       8    189.684692     29.626089      20.875      19.864      19.036 
      VR
       9    180.602478     23.990540      21.003      19.962      19.217 
      VR
      10    184.785507     26.824320      20.983      19.969      19.190 
      VR
      11    192.873947     29.601379      20.944      19.900      19.114 
      VR
      12    191.960449     32.390297      20.907      19.837      19.004 
      VR
      13    183.234314     29.591774      21.019      19.959      19.177 
      VR
      14    198.608170     32.404903      21.028      19.933      19.087 
      VR
      15    208.536697     32.404457      21.031      19.898      18.917 
      VR
      16    215.425766     35.189808      20.952      19.912      18.869 
      VR
      17    211.972580     35.169170      21.062      19.993      19.055 
      VR
      18    201.739838     35.234352      21.097      20.013      19.149 
      VR
      19    198.608170     32.404903      21.028      19.933      19.087 
      VR
      20    208.536697     32.404457      21.031      19.898      18.917 
      VR
      21    215.425766     35.189808      20.952      19.912      18.869 
      VR
      22    211.972580     35.169170      21.062      19.993      19.055 
      VR
      23    201.739838     35.234352      21.097      20.013      19.149 
      VR
      24    201.873154     32.386822      21.000      19.912      19.094 
      VR
      25    211.837280     32.391037      21.018      19.956      18.887 
      VR
      26    216.216324     37.998722      21.074      19.972      18.897 
      VR
      27    208.568130     35.197506      21.055      19.976      19.012 
      VR
      28    198.301239     35.218636      21.127      20.040      19.123 
      VR
      29    218.851593     35.218647      21.162      20.061      19.121 
      VR
      30    222.244431     35.193432      21.146      20.100      19.256 
      VR
      31    225.679306     35.158276      21.108      20.102      19.138 
      VR
      32    229.114594     35.154079      21.109      20.069      19.083 
      VR
      33    225.053543     29.585041      21.109      20.064      19.101 
      VR
      34    218.484024     32.397865      21.157      20.051      19.053 
      VR
      35    223.324417     38.002777      21.197      20.108      19.214 
      VR
      36    225.081039     32.366611      21.100      20.031      19.062 
      VR
      37    230.409027     37.977615      20.998      19.982      19.029 
      VR
      38    228.267899     29.562998      21.050      20.002      19.011 
      VR
      39    218.608292     29.590960      21.086      20.021      19.093 
      VR
      40    219.784576     38.000137      21.168      20.108      19.188 
      VR
      41    221.790970     32.360126      21.181      20.079      19.201 
      VR
      42    226.883743     37.952568      21.151      20.092      19.148 
      VR
      43    228.391403     32.370419      21.037      19.996      18.972 
      VR
      44    221.833221     29.593536      21.120      20.102      19.196 
      VR
      45    231.493652     29.561152      21.107      20.079      19.090 
      VR
      46    233.963348     37.967670      21.103      20.118      19.248 
      VR
      47    239.815979     40.776882      21.177      20.151      19.176 
      VR
      48    235.000549     32.369446      21.087      20.096      19.212 
      VR
      49    235.720306     23.978613      21.080      20.069      19.117 
      VR
      50    231.493652     29.561152      21.107      20.079      19.090 
      VR
      51    233.963348     37.967670      21.103      20.118      19.248 
      VR
      52    239.815979     40.776882      21.177      20.151      19.176 
      VR
      53    235.000549     32.369446      21.087      20.096      19.212 
      VR
      54    235.720306     23.978613      21.080      20.069      19.117 
      VR
      55    231.493652     29.561152      21.107      20.079      19.090 
      VR
      56    233.963348     37.967670      21.103      20.118      19.248 
      VR
      57    239.815979     40.776882      21.177      20.151      19.176 
      VR
      58    235.000549     32.369446      21.087      20.096      19.212 
      VR
      59    235.720306     23.978613      21.080      20.069      19.117 
      VR
      60    238.067291     26.742233      21.075      20.070      19.136 
      VR
      61    239.365143     35.179752      21.189      20.223      19.336 
      VR
      62    244.608307     37.976181      21.162      20.188      19.205 
      VR
      63    241.650742     32.340134      21.133      20.164      19.229 
      VR
      64    241.823608     23.950287      21.047      20.079      19.143 
      VR
      65    238.767471     23.968771      21.065      20.090      19.152 
      VR
      66    238.319641     32.363117      21.178      20.198      19.319 
      VR
      67    243.497925     40.747852      21.083      20.105      19.182 
      VR
      68    242.779221     35.157001      21.160      20.204      19.243 
      VR
      69    241.178314     26.761927      21.091      20.087      19.140 
      VR
      70    236.980118     21.171730      21.104      20.122      19.199 
      VR
      71    237.881577     29.548300      21.096      20.133      19.217 
      VR
      72    241.073135     37.950817      21.136      20.129      19.225 
      VR
      73    246.223633     35.124283      21.138      20.113      19.161 
      VR
      74    241.141617     29.572805      21.075      20.098      19.182 
      VR
      75    240.004684     21.128513      21.015      20.035      19.122 
      VR

Our vetting procedure based on image difference and machine learning 
have identified some known sources (thus unrelated to the GW event) such as

OPEM-19fl = AT 2019dje
Loading...
 
 
OPEM-19fj = SN 2019dek
OPEM-19fi = SN 2019dhc
OPEM-19fh = SN 2019dkx
OPEM-19fg = SN2019cdc
OPEM-19ff = AT 2019dku
Loading...
 
 
OPEM-19fe = SN 2019dod
OPEM-19ex = AT 2019dzt
Loading...
 
 
OPEM-19ev = AT 2018kud
Loading...
 
 
OPEM-19eu = AT 2019dxm
Loading...
 
 
OPEM-19eu = AT 2019dxm
Loading...
 
 
OPEM-19en = AT 2019cya
Loading...
 
  = ATLAS19ggy = ZTF19aaoyech
OPEM-19em = AT 2018ivk
Loading...
 
 

No interesting transient can be reported here. Detailed data analysis is 
still in progress and any interesting transient will be reported later.

Han-Jie Tan (NCU), Po-Chieh Yu (NCU), Atharva Sunil Patil (NCU),
Chow-Choong Ngeow (NCU), Albert Kong (NTHU), Wing-Huen Ip (NCU)

On behalf of Global Relay of Observatories Watching Transients Happen
(GROWTH) collaborations

We report observations of 58 galaxies in 90% localization of the BNS merger
candidate, S190425z, detected by LIGO/Virgo (GCN #24168
Loading...
 
 ) using the Lulin
One-meter Telescope (LOT) in Taiwan. The observation started at 2019-04-25
14:11:07 UT, ~5.9 hours after the trigger. All images were taken in R-band
with 180 second exposure time. No significant transient can be identified
brighter than R~20 mag (AB). The galaxy coordinates are listed below.

We thank the staff in Lulin Observatory for helping the observations.

195.2782  +39.841
195.8646  +53.532
196.3275  +31.442
197.0104  +53.936
200.6963  +32.623
206.5110  +55.716
206.5117  +55.715
212.2203  +33.532
212.8712  +55.122
214.8233  +35.138
216.1732  +55.706
217.8031  +35.332
220.4162  +36.647
221.4388  +32.630
224.0184  +45.405
225.3241  +31.875
226.3790  +30.911
229.1854  +7.0222
32.0402    +43.007
233.1953  +40.223
233.4227    +28.145
234.6793  +30.671
236.9750  +25.730
237.0115  +25.439
237.4094  +42.034
238.7582  +41.578
239.0813  +24.747
239.8704  +39.828
243.6089    +35.109
243.9256    +19.638
244.1279    +35.708
244.5305    +21.066
244.8738    +18.480
245.7836    +19.006
246.1423    +21.195
246.4086    +16.455
247.4369    +40.812
247.5337    +14.904
248.3241    +35.342
248.5431    +19.634
249.0647    +10.843
249.3963    +11.733
250.0136    +15.883
250.1398    +8.988
251.5005    +7.189
251.5155    +9.283
252.3932    +9.783
252.4388    +4.278
252.4483    +4.932
252.7889    +7.677
253.2453    +2.401
253.2702    -16.291
253.7912    +5.859
254.1937    -1.962
254.3263    +0.570
254.3493    -1.797
254.3984    -1.796
256.2616    -4.596

Y.-D. Hu, X.-Y.Li, I. Carrasco, E. Fernandez-Garcia and A. J. 
Castro-Tirado (IAA-CSIC), I. Carrasco, A. Castellon and C. Perez del 
Pulgar (UMA), D. Hiriart and W. H. Lee (UNAM), S. Jeong and I. H. Park 
(SKKU) and M. D. Caballero-Garcia (ASU-CAS, CZ) on behalf of a larger 
collaboration, report:

Following the detection of the GW S190425z (GCN 24168
Loading...
 
 ), the 60cm 
BOOTES-5/JGT robotic telescope at Observatorio Astronomico Nacional in 
San Pedro Martir (Mexico) observed 63 galaxies selected from the GLADE 
catalog in the LIGO/Virgo localization region (see D��lya and Raffai, GCN 
24171
Loading...
 
 ). Data was gathered starting on Apr 25, 12:26 UT (4.1 hr post GW) 
with a 20.5 limiting magnitude for each image (60s, clear filter). The 
list of observed galaxies is given below. No transients are detected in 
their vecinity. Further analysis is on its way.

We thank the staff at Observatorio Astronomico Nacional in San Pedro 
Martir for their excellent support.

Obstime(UTC)        Galaxy                RA(J2000) DEC(J2000)
2019-04-25T12:26:51 2MASS16593507+0857289 16:59:35 +08:59:30
2019-04-25T12:25:24 2MASS16590113+0600559 16:59:01 +06:02:57
2019-04-25T12:23:55 2MASS16550989+0551321 16:55:10 +05:53:33
2019-04-25T12:22:31 2MASS16551814+0745247 16:55:18 +07:47:26
2019-04-25T12:21:05 2MASS16535916+0615267 16:53:59 +06:17:28
2019-04-25T12:19:34 2MASS16565156+0534093 16:56:51 +05:36:10
2019-04-25T12:18:06 2MASS16523061+0947018 16:52:30 +09:49:03
2019-04-25T12:16:38 2MASS16562595+0556173 16:56:26 +05:58:19
2019-04-25T12:15:10 2MASS16505118+0847019 16:50:51 +08:49:03
2019-04-25T12:13:40 2MASS16462248+0902154 16:46:22 +09:04:16
2019-04-25T11:29:03 2MASS17074548+0304469 17:07:45 +03:06:48
2019-04-25T11:27:39 2MASS17071043+0115389 17:07:10 +01:17:40
2019-04-25T11:26:15 2MASS17070140+0140412 17:07:01 +01:42:43
2019-04-25T11:24:50 2MASS17063227+0325482 17:06:32 +03:27:50
2019-04-25T11:23:24 2MASS17061937+0413572 17:06:19 +04:15:58
2019-04-25T11:21:58 2MASS17055844+0122534 17:05:58 +01:24:54
2019-04-25T11:20:28 2MASS17052220+0452370 17:05:22 +04:54:38
2019-04-25T11:19:02 2MASS17084532+0141056 17:08:45 +01:43:07
2019-04-25T11:17:36 2MASS17091821+0126260 17:09:18 +01:28:27
2019-04-25T11:16:11 2MASS17043225+0120477 17:04:32 +01:22:49
2019-04-25T11:14:44 2MASS17034317+0414546 17:03:43 +04:16:56
2019-04-25T11:13:15 2MASS17082207+0057506 17:08:22 +00:59:52
2019-04-25T11:11:50 2MASS17083335+0255486 17:08:33 +02:57:50
2019-04-25T11:10:23 2MASS17081604+0356386 17:08:16 +03:58:40
2019-04-25T11:08:58 2MASS17064993+0214392 17:06:50 +02:16:40
2019-04-25T11:07:32 2MASS17082534+0256016 17:08:25 +02:58:03
2019-04-25T11:06:09 HyperLEDA59425        17:00:52 +02:08:06
2019-04-25T11:04:46 2MASS17001211+0149023 17:00:12 +01:51:03
2019-04-25T11:03:19 2MASS17052314+0453080 17:05:23 +04:55:09
2019-04-25T11:01:53 2MASS17045647+0032286 17:04:56 +00:34:30
2019-04-25T11:00:27 2MASS17042272+0033347 17:04:23 +00:35:36
2019-04-25T10:59:02 2MASS17044072+0225487 17:04:40 +02:27:50
2019-04-25T10:57:34 2MASS17034446+0025416 17:03:44 +00:27:43
2019-04-25T10:56:08 2MASS17033766+0032426 17:03:37 +00:34:43
2019-04-25T10:54:41 2MASS17012629+0142014 17:01:26 +01:44:03
2019-04-25T10:53:14 2MASS17005511+0249298 17:00:55 +02:51:31
2019-04-25T10:51:47 2MASS16575622+0309255 16:57:56 +03:11:27
2019-04-25T10:50:20 2MASS16572411+0039141 16:57:24 +00:41:15
2019-04-25T10:48:52 2MASS17034447+0515245 17:03:44 +05:17:26
2019-04-25T10:47:27 2MASS16591074+0307545 16:59:10 +03:09:56
2019-04-25T10:46:03 2MASS16573413+0256065 16:57:34 +02:58:08
2019-04-25T10:44:28 2MASS16585516+0107243 16:58:55 +01:09:25
2019-04-25T10:42:48 2MASS16573844+0037045 16:57:38 +00:39:06
2019-04-25T10:41:22 2MASS17034514+0145216 17:03:45 +01:47:23
2019-04-25T10:39:54 2MASS16594619+0230353 16:59:46 +02:32:36
2019-04-25T10:38:31 2MASS17014185+0202344 17:01:42 +02:04:35
2019-04-25T10:37:05 2MASS16591559+0121545 16:59:15 +01:23:56
2019-04-25T10:35:39 2MASS16550578+0259381 16:55:06 +03:01:39
2019-04-25T10:34:15 2MASS17005227+0206066 17:00:52 +02:08:08
2019-04-25T10:32:48 NGC6230               16:50:47 +04:38:17
2019-04-25T10:31:19 2MASS16541350+0501271 16:54:13 +05:03:28
2019-04-25T10:29:51 2MASS16521538+0343210 16:52:15 +03:45:22
2019-04-25T10:28:23 2MASS16521412+0314088 16:52:14 +03:16:10
2019-04-25T10:26:45 2MASS16514686+0334557 16:51:47 +03:36:57
2019-04-25T10:25:19 2MASS16504997+0437178 16:50:50 +04:39:19
2019-04-25T10:23:52 2MASS16503422+0505350 16:50:34 +05:07:36
2019-04-25T10:22:23 2MASS16494530+0416395 16:49:45 +04:18:41
2019-04-25T10:20:18 2MASS16503128+0209319 16:50:52 +02:11:33
2019-04-25T10:12:45 UGC10104              15:57:28 +30:05:37
2019-04-25T10:09:54 HyperLEDA1843124      15:47:24 +28:43:32
2019-04-25T10:06:46 2MASS15585202+2608083 15:58:52 +26:10:09
2019-04-25T10:05:17 2MASS15562377+2549058 15:56:23 +25:51:07
2019-04-25T09:57:38 SDSSJ160952.75+223818.6 16:09:53 +22:38:19

P. Short, M. Nicholl (Edinburgh), J. Anderson (ESO), T.-W. Chen (MPE), C. Inserra (Cardiff), O. Yaron (Weizmann), D. R. Young (QUB), C. Angus, M. Pursiainen, P. Wiseman (Southampton), S. Taubenberger (MPA), M. Gromadzki (Warsaw) on behalf of the ePESSTO+ collaboration

We obtained a spectrum of the transient PS19qu discovered by Pan-STARRS (Smith et al., GCN 24262
Loading...
 
 )  during follow-up of the gravitational wave trigger S190425z (GCN 24168
Loading...
 
 ) , under the advanced Public ESO Spectroscopic Survey for Transient Objects (ePESSTO+; see Smartt et al. 2015, A&A, 579, 40 http://www.pessto.org). The observations were performed on the ESO New Technology Telescope at La Silla with the EFOSC2 instrument.

The spectrum is host-galaxy dominated. It shows a star-forming galaxy at z=0.183, significantly further away than the peak of the distance posterior from the GW sky map (GCN 24168
Loading...
 
 ). At this redshift, the absolute magnitude implied by the Pan-STARRS detection is -18.9 mag.

[GCN OPS NOTE(27apr19): Per author's request, the "26c" in the Subject line and the "26z" in the first sentence
were changed to "25z".]

Wen-xiong Li (THU), Jun-cheng Chen(WZU), Xiaofeng Wang (THU), Kai Ye (YNAO), Ju-jia Zhang(YNAO), Chuan-jun Wang(YNAO), Jian-guo Wang(YNAO), Jin-ming Bai (YNAO), Jun Mo (THU),  Kaixin Lu(YNAO) , Michael Coughlin (Caltech), Sarah Antier (APC), Tianrui Sun (PMO), Lei Hu (PMO), and Lifan Wang (TAMU/PMO) report on behalf of a larger collaboration: 

Using the Lijiang 2.4-m telescope (LJT) at Yunnan Observatory, China, we observed the two candidates 
ZTF19aarykkb and ZTF19aarzaod reported by the Zwicky Transient Facility (Kasliwal et al., GCN 24191
Loading...
 
 ) 
as possible electromagnetic counterparts of  the GW event S190425z (LIGO/Virgo Collaboration, GCN 24168
Loading...
 
 ). 
Both have now been spectroscopically identified as type II SNe (Pavana et al., GCN 24200
Loading...
 
 ; Perley et al., 
GCN 24204
Loading...
 
 ; Buckley et al., GCN 24205
Loading...
 
 ; Izzo et al., GCN 24208
Loading...
 
 ; Wiersema et al., GCN 24209
Loading...
 
 ; Nicholl et al., 
GCN 24211
Loading...
 
 ). Multiple images were obtained with the LJT for these two SNe in g and r bands. Using the 
Pan-STARRS Survey images as templates for image subtraction, the results of PSF photometry for them 
are listed as

UT time:                       filter       mag(error)
-------------------------------------------------------
ZTF19aarykkb:
2019-04-25T17:56:45    g       19.14+-0.07
2019-04-25T17:58:07    r        18.36+-0.06
2019-04-25T20:57:24    g       19.04+-0.06
2019-04-25T20:58:56    r        18.50+-0.05
-------------------------------------------------------
ZTF19aarzaod:
2019-04-25T21:06:56    r        19.93+-0.12

These magnitudes are consistent with previous reports (Hiramatsu et al., GCN 24194
Loading...
 
 ; Tan et al., 
GCN 24193
Loading...
 
 ; Burke et al. GCN 24206
Loading...
 
 ; Kilpatrick et al. 24212; Sun et al. GCN 24234
Loading...
 
 ), and also 
consistent with the luminsoity of SNe II at a distance of about 110 Mpc after taking into the extinctions.

M. Axelsson (KTH & Stockholm Univ.), E. Bissaldi (INFN and Politecnico Bari), D. Kocevski (NASA/MSFC), F. Longo (University and INFN, Trieste), and N. Omodei (Stanford Univ.) report on behalf of the Fermi-LAT Collaboration:

We have searched data collected by the Fermi Large Area Telescope (LAT) on April 25, 2019, for possible high-energy (E > 100 MeV) gamma-ray emission in spatial/temporal coincidence with the LIGO/Virgo trigger S190425z (GCN 24168
Loading...
 
 ).

We define "instantaneous coverage" as the integral over the region of the LIGO probability map that is within the LAT field of view at a given a time, and "cumulative coverage" as the integral of the instantaneous coverage over time. Fermi-LAT had instantaneous coverage of ~37% of the LIGO probability at the time of the trigger (T0 = 2019-04-25 08:18:05.017 UTC), and reached ~98% cumulative coverage after ~4 ks. Due to the observing pattern of Fermi, the remaining area was not observed for more than 24 hours after the trigger time of the event.

We performed a search for a transient counterpart within the observed region of the 90% contour of the LIGO map in a fixed time window from T0 to T0 + 10 ks.

Two significant excesses (with TS>25) were found at R.A., Dec. = 278.7, -21.1 and 57.2, -28.2, respectively, but they are associated with known sources currently flaring (PKS 1830-211 and PKS 0346-27).

We also performed a search which adapted the time interval of the analysis to the exposure of each region of the sky, and no additional excesses were found.

Energy flux upper bounds for the fixed time interval between 100 MeV and 100 GeV for this search vary between 0.7e-10 and 3.9e-8 [erg/cm^2/s].

The Fermi-LAT point of contact for this event is Magnus Axelsson (magaxe@kth.se<mailto:magaxe@kth.se>).

The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.

K. W. Smith, D. R. Young, O. McBrien, J. Gillanders. S. Srivastav,
S. J. Smartt, D. O'Neil, P. Clark, S. Sim (QUB), K. C. Chambers,
M. Huber, E. Magnier, A. Schultz, (IfA, Univ. Hawaii), L. Denneau,
H. Flewelling, A. Heinze, J. Tonry, H. Weiland, A. Rest (STScI),
B. Stalder (LSST), C. Stubbs (Harvard)

Due to delayed ingest of a small amount of data from the Pan-STARRS1 telescope
(Chambers et al. 2016, arXiv:1612.05560
Loading...
 
 C), we report 5 candidates in addition
to those already announced in GCN 24210
Loading...
 
 . bPC denotes the probability
contour within which the transient is found according to the S190425z LAL
Interference map (Singer, GCN 24228
Loading...
 
 ).

Name   | TNS Name  | RA (J2000)  | Dec (J2000) |   z   | Disc mag | bPC | Notes
PS19qx | AT2019edd
Loading...
 
  | 15:17:03.75 | +29:57:33.7 |       | 20.92 i  |  40 |
PS19qt | AT2019edc
Loading...
 
  | 15:24:13.95 | +28:54:47.8 | 0.075 | 21.23 i  |  50 | (1)
PS19qu | AT2019edf
Loading...
 
  | 16:01:49.91 | +22:00:17.4 |       | 20.90 i  |  60 |
PS19qv | AT2019ecy
Loading...
 
  | 16:14:20.12 | +31:21:20.3 | 0.179 | 21.08 i  |  90 | (2)
PS19rg | AT2019eda
Loading...
 
  | 16:25:34.93 | +34:08:40.8 |       | 20.98 i  |  90 |

NOTES
(1) Probable host is 2MASX J15241346+2854453 (NED)
(2) Probable host is SDSS J161420.36+312121.5 (NED)

Finders can be found at:
https://star.pst.qub.ac.uk/~kws/finders/S190425z/ps1_finders.tgz

Seo-Won Chang (ANU/OzGrav), Christian Wolf (ANU/OzGrav), Christopher A. Onken (ANU), Susan Scott (ANU/OzGrav), Christopher Lidman (ANU), J.Cooke (Swinburne), S.Webb (Swinburne), P.Gurri (Swinburne), T.Nordlander (ANU).

We obtained a series of early IFU spectra of the potential counterpart ZTF19aarykkb (Kasliwal et al., GCN 24191
Loading...
 
 ) to the GW candidate S190525z (GCN 24168
Loading...
 
 ) and host galaxy with the WiFeS instrument on the ANU2.3m telescope, located at Siding Springs Observatory, Australia. We acquired our first 850s exposure integration starting at UT 2019-04-25T17:40:40.5 together with 5x1200s spectra, using a configuration of R3000/RT560 covering the wavelength range of 330nm to 900nm. The spectrum appears to be a young Type II supernova, consistent with Pavana (GCN 24200
Loading...
 
 ), Perley (GCN 24204
Loading...
 
 ) and Dichiara (GCN 24220
Loading...
 
 ).

E. Howell (OzGrav-UWA), N. Christensen (Artemis), M. Blazek 
(HETH/IAA-CSIC), M. Vardosanidze (Iliauni), A. Klotz (IRAP), J. P. Teng 
(AGORA), S. Perrigault (AGORA), P. Thierry (Auragne obs.), P. Fock-Hang 
(AGORA), A. Baransky (Kyiv univ), K. Barynova (Kyiv univ), A. Simon 
(ASPD TSNUK), V. Vasylenko (Kyiv univ), V.Aivazyan (Iliauni), S. Beradze 
(Iliauni), R. Inasaridze (Iliauni), N. Kochiashvili (Iliauni), R. 
Natsvlishvili (Iliauni), G. Kapanadze (Iliauni), S. Antier (APC), S. 
Basa (LAM), M. Boer (Artemis), D. Corre (LAL), M. Coughlin (Caltech), D. 
Coward (OzGrav-UWA), J.G. Ducoin (LAL), B. Gendre (OzGrav-UWA), P. Hello 
(LAL), C. Lachaud (APC), N. Leroy (LAL), D. Turpin (NAOC), X. Wang 
(THU), and X. Zhang (THU)

report on behalf of the Les Makes, Abastumani, Lisnyky and GRANDMA 
collaborations.

We performed galaxy-targeted observations of the LIGO/Virgo S190425z 
event (GCN #24168
Loading...
 
 ) with the Les Makes-T60 telescope located in La 
Reunion-France, Abastumani-T70 telescope located in Abastumani 
Astrophysical Observatory, and AZT-8 telescope located in Observational 
Station Lisnyky of TSNU of Kyiv.

The target galaxies are selected from the list of potential host 
galaxies from the GLADE catalog in the 90% credible area of the 
localization region of the LIGO/Virgo GW event. Note that these galaxies 
are compatible within 3 sigma for the distance given by GW event.

The list of the galaxies we observed is shown in the tables below. 
TStart and TEnd refers respectively to the time of the first and last 
exposure for a given galaxy. Observations are not necessarily continuous 
in this interval.

Les Makes-T60 cm imaged 52 galaxies in clear filter. The observation 
started on 04/25/19 15:18:10 UTC which corresponds approximately to 421 
minutes after the GW trigger time. The typical limiting magnitude is 
19.2 for a 180 s exposure.


+------------+------------+-----------------------+-------+--------+------+
| TStart     | TEnd       | Galaxy                | RA    | DEC    | 
Dist.|
| [UTC]      | [UTC]      | name                  | [deg] | [deg]  | 
[Mpc]|
|------------+------------+-----------------------+-------+--------+------|
| 2019-04-25 | 2019-04-25 | GWGC [MFB2005]        |182.081| 25.233 | 
105.2|
| 15:18:10   | 15:33:35   | J120819.37+251357.9   |       |        |     
  |
| 2019-04-25 | 2019-04-25 | HyperLEDA             |181.979| 25.017 | 
106.3|
| 15:34:40   | 15:50:05   |SDSSJ120754.97+250102.6|       |        |     
  |
| 2019-04-25 | 2019-04-25 | HyperLEDA             |181.978| 25.101 | 111 
  |
| 15:34:40   | 15:50:05   |SDSSJ120754.70+250604.8|       |        |     
  |
| 2019-04-25 | 2019-04-25 | HyperLEDA 38516       |182.038| 25.079 | 
111.7|
| 15:34:40   | 15:50:05   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-26 | HyperLEDA 1109773     |254.435| -1.799 | 
136.9|
| 21:58:35   | 00:50:20   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-26 | 2MASS 16574427-0147567|254.434| -1.799 | 
136.4|
| 21:58:35   | 00:50:20   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | 2MASS 16573561-0147457|254.398| -1.796 | 
142.6|
| 21:58:35   | 22:14:00   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | HyperLEDA 1109835     |254.399| -1.796 | 
145.1|
| 21:58:35   | 22:14:00   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | 2MASS 16572382-0147498|254.349| -1.797 | 
147.9|
| 21:58:35   | 22:14:00   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | HyperLEDA 1110982     |254.423| -1.754 | 
148.8|
| 21:58:35   | 22:14:00   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | HyperLEDA 1109807     |254.349| -1.797 | 
148.8|
| 21:58:35   | 22:14:00   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | 2MASS 16574141-0145157|254.423| -1.754 | 
168.5|
| 21:58:35   | 22:14:00   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | HyperLEDA 1106076     |254.456| -1.934 | 
136.3|
| 22:14:10   | 22:29:35   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | 2MASS 16574955-0156027|254.456| -1.934 | 
135.6|
| 22:14:10   | 22:29:35   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | 2MASS 16573281-0138287|254.387| -1.641 | 
157.3|
| 22:29:45   | 22:45:10   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | 2MASS 16570522-0151022|254.272| -1.851 | 
147.2|
| 22:45:21   | 23:00:46   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | HyperLEDA 1107232     |254.346| -1.89  | 
148.8|
| 22:45:21   | 23:00:46   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | HyperLEDA 1109171     |254.296| -1.82  | 
148.8|
| 22:45:21   | 23:00:46   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | 2MASS 16572303-0153258|254.346| -1.891 | 
155.8|
| 22:45:21   | 23:00:46   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | 2MASS 16571094-0149128|254.296| -1.82  | 
169.9|
| 22:45:21   | 23:00:46   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-26 | 2MASS 16580368-0150074|254.515| -1.835 | 
147.5|
| 23:00:56   | 00:50:20   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | HyperLEDA 1108643     |254.598| -1.839 | 
136.9|
| 23:00:56   | 23:16:21   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-26 | 2MASS 16580515-0149544|254.521| -1.832 | 
162.3|
| 23:00:56   | 00:50:20   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | 2MASS 16585823-0202277|254.743| -2.041 | 
132.1|
| 23:16:31   | 23:31:56   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | HyperLEDA 161011      |254.743| -2.041 | 145 
  |
| 23:16:31   | 23:31:56   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | HyperLEDA 161014      |254.822| -2.074 | 
120.5|
| 23:16:31   | 23:31:56   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | 2MASS 16591729-0204281|254.822| -2.074 | 
107.3|
| 23:16:31   | 23:31:56   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | HyperLEDA 161013      |254.775| -1.914 | 
133.6|
| 23:32:06   | 23:47:31   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | 2MASS 16592042-0153111|254.835| -1.886 | 147 
  |
| 23:32:06   | 23:47:31   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | HyperLEDA 161015      |254.835| -1.886 | 
148.1|
| 23:32:06   | 23:47:31   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | 2MASS 16590588-0154501|254.775| -1.914 | 
128.1|
| 23:32:06   | 23:47:31   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-26 | HyperLEDA             |253.592| -16.81 | 
122.3|
| 23:47:49   | 00:03:14   | 6dFJ1654221-164837    |       |        |     
  |
| 2019-04-25 | 2019-04-26 | 2MASS                 |253.592| -16.81 | 
122.5|
| 23:47:49   | 00:03:14   | 16542215-1648370      |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 1093975     |255.095| -2.372 | 
140.4|
| 00:03:31   | 00:18:56   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 161019      |255.096| -2.326 | 
143.6|
| 00:03:31   | 00:18:56   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 1092764     |255.06 | -2.413 | 145 
  |
| 00:03:31   | 00:18:56   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | 2MASS 17002062-0225482|255.086| -2.43  | 
145.6|
| 00:03:31   | 00:18:56   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | 2MASS 17002302-0219322|255.096| -2.326 | 129 
  |
| 00:03:31   | 00:18:56   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | 2MASS 17001441-0224462|255.06 | -2.413 | 
147.4|
| 00:03:31   | 00:18:56   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | 2MASS 17002095-0217192|255.087| -2.289 | 
151.5|
| 00:03:31   | 00:18:56   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | 2MASS 17002288-0222202|255.095| -2.372 | 
120.1|
| 00:03:31   | 00:18:56   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 899699      |253.301| -16.316| 
118.8|
| 00:19:13   | 00:34:38   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 899284      |253.355| -16.349| 
118.8|
| 00:19:13   | 00:34:38   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 900018      |253.27 | -16.291| 
122.8|
| 00:19:13   | 00:34:38   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | 2MASS 16530485-1617273|253.27 | -16.291| 123 
  |
| 00:19:13   | 00:34:38   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | 2MASS 16532193-1617132|253.341| -16.287| 
129.8|
| 00:19:13   | 00:34:38   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | 2MASS 16531513-1621223|253.313| -16.356|  
99.7|
| 00:19:13   | 00:34:38   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 1109100     |254.506| -1.823 | 138 
  |
| 00:34:55   | 00:50:20   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | 2MASS 16580128-0149216|254.505| -1.823 | 
136.4|
| 00:34:55   | 00:50:20   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 161003      |253.86 | -7.206 | 
132.3|
| 00:50:34   | 01:05:59   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | 2MASS 16552449-0715255|253.852| -7.257 | 
130.1|
| 00:50:34   | 01:05:59   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 161002      |253.852| -7.257 | 
130.7|
| 00:50:34   | 01:05:59   |                       |       |        |     
  |
+------------+------------+-----------------------+-------+--------+------+


Abastumani-T70 imaged 41 galaxies in R filter. The observation started 
on 04/25/19 23:08:01 UTC which corresponds approximately to 890 minutes 
after the GW trigger time. The typical limiting magnitude is 16.5 for a 
1 min exposure.


+------------+------------+-----------------------+-------+--------+------+
| TStart     | TEnd       | Galaxy                | RA    | DEC    | 
Dist.|
| [UTC]      | [UTC]      | name                  | [deg] | [deg]  | 
[Mpc]|
|------------+------------+-----------------------+-------+--------+------|
| 2019-04-25 | 2019-04-25 | GWGC UGC07124         |182.193| 24.946 | 
100.5|
| 23:08:01   | 23:15:13   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | GWGC PGC038615        |182.325| 24.968 | 
102.7|
| 23:08:01   | 23:15:13   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | GWGC PGC038526        |182.055| 24.943 | 
105.7|
| 23:08:01   | 23:15:13   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | HyperLEDA 1093975     |255.095| -2.372   
140.4|
| 23:22:46   | 23:29:58   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | HyperLEDA 161019      |255.096| -2.326 | 
143.6|
| 23:22:46   | 23:29:58   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | HyperLEDA 1092764     |255.06 | -2.413 | 145 
  |
| 23:22:46   | 23:29:58   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | 2MASS 17002062-0225482|255.086| -2.43  | 
145.6|
| 23:22:46   | 23:29:58   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | 2MASS 17002302-0219322|255.096| -2.326 | 129 
  |
| 23:22:46   | 23:29:58   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | 2MASS 17001441-0224462|255.06 | -2.413 | 
147.4|
| 23:22:46   | 23:29:58   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | 2MASS 17002095-0217192|255.087| -2.289 | 
151.5|
| 23:22:46   | 23:29:58   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | 2MASS 17002288-0222202|255.095| -2.372 | 
120.1|
| 23:22:46   | 23:29:58   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | HyperLEDA 899699      |253.301| -16.316| 
118.8|
| 23:37:08   | 23:44:20   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | HyperLEDA 899284      |253.355| -16.349| 
118.8|
| 23:37:08   | 23:44:20   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | HyperLEDA 900018      |253.27 | -16.291| 
122.8|
| 23:37:08   | 23:44:20   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | 2MASS 16530485-1617273|253.27 | -16.291| 123 
  |
| 23:37:08   | 23:44:20   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | 2MASS 16532193-1617132|253.341| -16.287| 
129.8|
| 23:37:08   | 23:44:20   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | 2MASS 16531513-1621223|253.313| -16.356|  
99.7|
| 23:37:08   | 23:44:20   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-26 | HyperLEDA             |253.486| -16.12 | 
121.9|
| 23:54:01   | 00:01:13   | 6dFJ1653567-160711    |       |        |     
  |
| 2019-04-25 | 2019-04-26 | 2MASS 16535674-1607110|253.486| -16.12 | 
122.1|
| 23:54:01   | 00:01:13   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-26 | 2MASS 16535385-1614537|253.474| -16.248| 
109.3|
| 23:54:01   | 00:01:13   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 896696      |253.494| -16.552| 
121.4|
| 00:04:49   | 00:12:01   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | 2MASS 17005715-0225086|255.238| -2.419 | 127 
  |
| 00:17:30   | 00:24:42   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | 2MASS 17012357-0220366|255.348| -2.344 | 
146.1|
| 00:17:30   | 00:24:42   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 1094718     |255.348| -2.344 | 
150.5|
| 00:17:30   | 00:24:42   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 1697461     |241.489| 23.986 | 
148.8|
| 00:30:30   | 00:37:42   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 1696139     |241.357| 23.92  | 
136.9|
| 00:30:30   | 00:37:42   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA             |235.784| 28.419 | 145 
  |
| 00:42:34   | 00:49:45   |SDSSJ154308.15+282509.9|       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 1835553     |235.651| 28.432 | 
143.7|
| 00:42:34   | 00:49:45   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 1697264     |240.942| 23.977 | 
157.7|
| 00:55:56   | 01:03:07   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 1695306     |240.892| 23.875 | 
153.6|
| 00:55:56   | 01:03:07   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 56887       |240.925| 24.095 | 
140.9|
| 00:55:56   | 01:03:07   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 56963       |241.153| 23.663 | 
165.5|
| 01:09:56   | 01:17:08   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 1691288     |241.25 | 23.658 | 
166.8|
| 01:09:56   | 01:17:08   |            |          |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 1693165     |241.235| 23.758 | 
170.6|
| 01:09:56   | 01:17:08   |            |          |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 1690684     |241.15 | 23.625 | 
163.5|
| 01:09:56   | 01:17:08   |            |          |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 57021       |241.26 | 23.669 | 
146.9|
| 01:09:56   | 01:17:08   |            |          |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 1690441     |241.184| 23.612 | 
151.4|
| 01:09:56   | 01:17:08   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA             |241.04 | 24.331 | 
168.7|
| 01:21:42   | 01:28:54   |SDSSJ160409.58+241950.7|       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 1706506     |240.988| 24.402 | 
169.4|
| 01:21:42   | 01:28:54   |           |           |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 1706072     |241.077| 24.382 | 
151.9|
| 01:21:42   | 01:28:54   |            |          |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 1703751     |241.076| 24.281 | 
147.3|
| 01:21:42   | 01:28:54   |                       |       |        |     
  |
+------------+------------+-----------------------+-------+--------+------+


AZT-8 imaged 26 galaxies, in R and B filters. The observation started on 
04/25/19 22:32:38 UTC which corresponds approximately to 855 minutes 
after the GW trigger time. The typical limiting magnitude is 19.2 for a 
20x30 s exposure.


+------------+------------+-----------------------+-------+--------+------+
| TStart     | TEnd       | Galaxy                | RA    | DEC    | 
Dist.|
| [UTC]      | [UTC]      | name                  | [deg] | [deg]  | 
[Mpc]|
|------------+------------+-----------------------+-------+--------+------|
| 2019-04-25 | 2019-04-25 | HyperLEDA 1107232     |254.346| -1.89  | 
148.8|
| 22:32:38   | 22:56:24   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | 2MASS 16572303-0153258|254.346| -1.891 | 
155.8|
| 22:32:38   | 22:56:24   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | 2MASS 16570522-0151022|254.272| -1.851   
147.2|
| 23:01:18   | 23:21:22   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | HyperLEDA 1109171     |254.296| -1.82    
148.8|
| 23:01:18   | 23:21:22   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | 2MASS 16571094-0149128|254.296| -1.82  | 
169.9|
| 23:01:18   | 23:21:22   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | HyperLEDA 1109773     |254.435| -1.799 | 
136.9|
| 23:24:57   | 23:45:08   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | 2MASS 16574427-0147567|254.434| -1.799 | 
136.4|
| 23:24:57   | 23:45:08   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | 2MASS 16573561-0147457|254.398| -1.796 | 
142.6|
| 23:24:57   | 23:45:08   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | HyperLEDA 1109835     |254.399| -1.796 | 
145.1|
| 23:24:57   | 23:45:08   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | 2MASS 16572382-0147498|254.349| -1.797 | 
147.9|
| 23:24:57   | 23:45:08   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | HyperLEDA 1110982     |254.423| -1.754 | 
148.8|
| 23:24:57   | 23:45:08   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | HyperLEDA 1109807     |254.349| -1.797 | 
148.8|
| 23:24:57   | 23:45:08   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-25 | 2MASS 16574141-0145157|254.423| -1.754 | 
168.5|
| 23:24:57   | 23:45:08   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-26 | HyperLEDA 1699170     |241.231| 24.073 | 
165.3|
| 23:56:12   | 00:16:25   |                       |       |        |     
  |
| 2019-04-25 | 2019-04-26 | HyperLEDA             |241.268| 24.045 | 
154.1|
| 23:56:12   | 00:16:25   |SDSSJ160504.21+240240.4|       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 140564      |241.215| 23.938 | 
161.5|
| 00:17:33   | 00:37:36   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 1695387     |241.253| 23.879 | 
154.2|
| 00:17:33   | 00:37:36   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA             |241.229| 23.919 | 146 
  |
| 00:17:33   | 00:37:36   |SDSSJ160454.83+235507.5|       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 57003       |241.211| 23.975 | 
176.2|
| 00:17:33   | 00:37:36   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA NGC6051     |241.236| 23.933 | 
143.6|
| 00:17:33   | 00:37:36   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 57014       |241.248| 23.97  | 
140.2|
| 00:17:33   | 00:37:36   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 1697461     |241.489| 23.986 | 
148.8|
| 00:40:37   | 01:01:06   |                       |       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA             |241.333| 23.915 | 
149.7|
| 01:03:45   | 01:24:03   |SDSSJ160519.85+235455.0|       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA             |241.275| 23.874 | 
175.9|
| 01:03:45   | 01:24:03   |SDSSJ160505.95+235227.2|       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA             |241.301| 23.853 | 
136.9|
| 01:03:45   | 01:24:03   |SDSSJ160512.22+235109.2|       |        |     
  |
| 2019-04-26 | 2019-04-26 | HyperLEDA 1696139     |241.357| 23.92  | 
136.9|
| 01:03:45   | 01:24:03   |                       |       |        |     
  |
+------------+------------+-----------------------+-------+--------+------+


GRANDMA (Global Rapid Advanced Network Devoted to the Multi-messenger 
Addicts) is a network of robotic telescopes connected all over the world 
with both photometry and spectrometry capabilities for Time-domain 
Astronomy (https://grandma.lal.in2p3.fr/). Details on the telescopes are 
available on the GRANDMA web pages.

This circular is citable.

R. Carini (INAF-OAR), L. Izzo (IAA), E. Palazzi (INAF-OAS), D. Sand (U of
Arizona), A. Rossi (INAF-OAS), L. Cassar�� (INAF-IASF Mi), A. Gargiulo
(INAF-IASF Mi), P. D'Avanzo (INAF-OAB), A. Melandri  (INAF-OAB), L.
Tomasella (INAF-OAPd), S. Benetti (INAF-OAPd), M.T. Botticella
(INAF-OAC), M. Branchesi (GSSI), V. D'Elia (ASI-SSDC), E. Brocato
(INAF-OAAb, INAF-OAR), M. Della Valle (INAF-OAPd), G. Greco (Univ.
Urbino), O. Kuhn (LBTO), I. Shivaei (U of Arizona), X. Fan (U of
Arizona), J. Andrews (U of Arizona), W.-F. Fong (Northwestern), K. Paterson
(Northwestern), M. Lundquist (U of Arizona), F. Cusano (INAF-OAS) on behalf
of GRAWITA report:



We observed the transient source AT2019ebq
Loading...
 
 /PS19qp reported by Pan-STARRS
(Smith, et al., GCN 24210
Loading...
 
 ) within the skymap of the GW event S190425z (GCN
24168
Loading...
 
 ) with the two 8.4 m telescopes of the Large Binocular Telescope (LBT,
Mount Graham, Arizona) equipped with the MODS1 and MODS2 cameras in
spectroscopic mode. The observations started on 2019-04-26 at 11:00:44 UT.
Four optical spectra, lasting 600 s each, were obtained using the dual
grating (wavelength range ~ 320-1000 nm).

The combined spectrum has a low S/N. A classification attempt performed
with GELATO (Harutyunyan et al., 2008, A&A, 488, 383) shows that the
spectrum is similar to those of type Ib/c SNe few days after the maximum.
Our results are in agreement with the findings of Morokuma et al. (GCN
24230
Loading...
 
 ) and Jencson et al. (GCN 24233
Loading...
 
 ).



We thank the LBT team for the observations.

[GCN OPS NOTE(27apr19): Per author's request, Kuhn's affilliation was changed
to LBTO.]

G. Hosseinzadeh, E. Berger, P. K. Blanchard, T. Eftekhari, J. Gill,
S. Gomez, L. Patton, V. A. Villar, P. K. G. Williams (Harvard U),
P. S. Cowperthwaite (Carnegie Obs), R. Chornock (Ohio U), W. Fong, 
R. Margutti (Northwestern U), and M. Nicholl (U Edinburgh) report:

We obtained 30 s i-band images of the following GLADE galaxies (Dalya
et al. 2018, MNRAS, 479, 2374) in the LIGO/Virgo localization region of
S190425z (GCN 24168
Loading...
 
 ) with the MMTCam instrument on the MMT 6.5-m telescope:

Name              R.A. Dec.      Date UT
16590728-0544311  254.780334 -5.741986  2019-04-26 08:30:29.18
58987.0           251.852000 -20.141740  2019-04-26 08:32:14.13
NGC6224           252.077301 6.312206  2019-04-26 08:34:11.44
NGC6051           241.236267 23.932871  2019-04-26 08:36:36.52
IC4572            235.475815 28.134085  2019-04-26 08:40:22.72
UGC10320          244.530502 21.066381  2019-04-26 08:44:29.81
IC4569            235.201462 28.292059  2019-04-26 08:47:01.76
57607             243.740997 21.938314  2019-04-26 08:50:10.58
57472             243.084732 23.001947  2019-04-26 08:51:40.62
IC1219            246.114319 19.482584  2019-04-26 08:53:28.45
UGC10412          247.400574 15.658440  2019-04-26 08:55:23.95
NGC6001           236.941498 28.641853  2019-04-26 08:57:41.17
55883             235.941849 28.415155  2019-04-26 08:59:38.86
57645             243.925613 19.637508  2019-04-26 09:02:13.12
59121             252.840240 7.862305  2019-04-26 09:04:08.24
56949             241.148224 25.189823  2019-04-26 09:06:30.33
58860             251.038666 7.445273  2019-04-26 09:08:30.08
57542             243.441711 22.918877  2019-04-26 09:10:43.92
UGC10224          242.209320 22.042635  2019-04-26 09:13:35.96
58097             246.408646 16.455000  2019-04-26 09:16:56.83
1717114           241.067825 24.812338  2019-04-26 09:18:57.27
59239.0           253.600113 -9.889244  2019-04-26 09:22:17.77
UGC10260          242.991150 20.923468  2019-04-26 09:25:28.05
IC4570            235.343994 28.229799  2019-04-26 09:28:54.53
UGC10035          236.901474 26.063671  2019-04-26 09:42:06.86
57692             244.190460 19.521360  2019-04-26 09:46:51.23
16505342-1500143  252.722595 -15.003985  2019-04-26 09:49:19.19
NGC6240           253.245255 2.400985  2019-04-26 09:51:26.55
UGC10360          245.797256 16.932606  2019-04-26 09:53:38.27
55774             235.152664 28.512449  2019-04-26 09:56:11.90
58735             250.167572 14.351479  2019-04-26 09:58:49.71
IC4621            252.713272 8.783868  2019-04-26 10:00:50.14
NGC6075           242.844025 23.965147  2019-04-26 10:04:43.26
16582619-0319463  254.609146 -3.329548  2019-04-26 10:11:41.89
16073961+2220315  241.915070 22.342087  2019-04-26 10:15:39.64
58028             246.063141 20.183607  2019-04-26 10:17:29.71
54895.0           230.687134 29.769716  2019-04-26 10:19:52.41
IC4505            221.639069 33.408661  2019-04-26 10:21:51.85
58768             250.337082 8.909049  2019-04-26 10:24:47.75
55373             233.193909 28.367073  2019-04-26 10:27:25.07
IC4587            239.965057 25.940653  2019-04-26 10:29:21.52
UGC08145          195.576172 32.890778  2019-04-26 10:31:26.07
57293             242.276917 24.870296  2019-04-26 10:35:04.99
16540875-0738073  253.536499 -7.635365  2019-04-26 10:38:59.44
52138             218.826752 35.118813  2019-04-26 10:41:49.85
16153554+1927123  243.898087 19.453444  2019-04-26 10:44:25.24
59338.0           254.524000 -21.274100  2019-04-26 10:46:46.58
UGC09233          216.145950 35.279827  2019-04-26 10:50:02.28
56421             239.016144 24.447973  2019-04-26 10:52:11.64
1484188           247.218430 15.420772  2019-04-26 10:54:30.92

Comparison of the images to the PS1 3pi survey (Chambers et al. 2016, 
arXiv:1612.05560
Loading...
 
 ) reveals no new sources brighter than ~21 mag within
the 2.7 arcmin field of view.

We thank Chun Ly and Ben Kunk at MMT for taking these observations and
Dallan Porter for help with the target submission.

V. Lipunov, E. Gorbovskoy, N.Tyurina, V.Kornilov, D.Vlasenko, V.Vladimirov, 
D.Zimnukhov,
A.Kuznetsov, P.Balanutsa, A. Chasovnikov, V.Topolev, D.Kuvshinov, F.Balakin 
(Lomonosov Moscow State University, SAI, Physics Department),

V.B. Petkov, M.M. Boliev, A.N. Kurenya,
Baksan Neutrino Observatory, Institute for Nuclear Research of RAS,
Moscow, Russia

R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres (The Instituto 
de Astrofisica de Canarias),

D. Buckley (South African Astronomical Observatory),

O. Gress, N.M. Budnev, O.Ershova (Applied Physics Institute, Irkutsk State 
University),

V. Yurkov, A. Gabovich, Yu. Sergienko, D. Kobcev (Blagoveschensk Educational 
State University),


A. Tlatov, V.Senik, A.V. Parhomenko, D. Dormidontov (Kislovodsk Solar Station 
of the Pulkovo Observatory),

R. Podesta, C. Lopez, C.Francile, F. Podesta (Observatorio Astronomico Felix 
Aguilar OAFA, San Juan National University),

H.Levato (Instituto de Ciencias Astronomicas, de la Tierra y del Espacio ICATE 
SJNU)

MASTER Global Robotic Net (http://observ.pereplet.ru, Lipunov et al., 
2010,Advances in Astronomy,vol. 2010, 30L)
started  LIGO/Virgo S190425z (Singer et al. GCN 24168
Loading...
 
 )
inspection at 2019-04-25 09:10:18 UT (Lipunov et al. GCN 24167
Loading...
 
 ) at 
MASTER-OAFA (Argentina).

MASTER-OAFA started PS19qp (Smith et al., GCN 24210
Loading...
 
  ) at  2019-04-26 
01:56:40.

         Looking at our old images AT2019ebq
Loading...
 
  / PS19qp, we 
found a very recent inspection of this field due to the neutrino BNO alert 
3 weeks ago and automatical Circular (not published yet).

To establish a possible connection of this supernova with neutrinos, it is 
extremely important to determine the age of the supernova AT2019ebq
Loading...
 
  / 
PS19qp . Thus the object is not associated with LIGO/Virgo S190425z but 
may be connected with BNO Alert190405.62 .

Below you can find automatic Circular (not published yet):

MASTER-Kislovodsk robotic telescope  (Global MASTER-Net: 
http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, 
vol. 2010, 30L)  located in Russia (Lomonosov MSU, Kislovodsk Solar 
Station of Pulkovo observatory) was pointed to the  BAKSAN Alert190405.62 
( 17h 25m 36.00s , - 2d 36m 00.00s, R=3) 19864 sec after trigger time at 
2019-04-05 20:29:29 UT, with upper limit up to  19.2 mag. The observations 
began at zenit distance = 83 deg. The sun  altitude  is -39.9 deg.

MASTER-Tavrida robotic telescope  located in Russia (Lomonosov MSU, SAI 
Crimea astronomical station) was pointed to the  BAKSAN Alert190405.62 
28940 sec after trigger time at 2019-04-05 23:00:45 UT, with upper limit 
up to  19.1 mag. The observations began at zenit distance = 63 deg. The 
sun  altitude  is -37.1 deg.

MASTER-SAAO robotic telescope  located in South Africa (South African 
Astronomical Observatory) was pointed to the  BAKSAN Alert190405.62 1 days 
39324 sec after trigger time at 2019-04-07 01:53:49 UT, with upper limit 
up to  19.2 mag. The observations began at zenit distance = 34 deg. The 
sun  altitude  is -38.5 deg.

MASTER-OAFA robotic telescope  located in Argentina (OAFA observatory of 
San Juan National University) was pointed to the  BAKSAN Alert190405.62 1 
days 54872 sec after trigger time at 2019-04-07 06:12:57 UT, with upper 
limit up to  18.0 mag. The observations began at zenit distance = 49 deg. 
The sun  altitude  is -56.9 deg.

The galactic latitude b = -60 deg., longitude l = 98 deg.


Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=991224

The follow up spectral and photometric observations of AT2019ebq
Loading...
 
 /PS19qp 
are required.


This message may be cited

J. Alvarez-Muniz, F. Pedreira, E. Zas (Univ. Santiago de Compostela, Spain),
K. H. Kampert & M. Schimp (Bergische Universitat, Wuppertal, Germany)
on behalf of the Pierre Auger Collaboration.

In response to:
LIGO/Virgo GW trigger S190425z
T0=2019-04-25 08:18:05 UTC

We searched for Ultra-High-Energy (UHE) neutrinos with energies
above ~ 1e17 eV in data collected with the Surface Detector (SD)
of the Pierre Auger Observatory in a [-500,500] second interval
about the LIGO-Virgo trigger S1902425z as well as 1 day after it.

The field of view (fov) where the SD of Auger is sensitive to UHE
neutrinos (corresponding to inclined directions with respect to the
vertical relative to the ground) was PARTIALLY COINCIDENT (35.5%) with
the LIGO 90% localization region at the time T0 of the merger alert.

NO events survived the cuts applied to reject the background due
to UHE Cosmic Rays i.e. NO neutrino candidates were detected.

-------
The Pierre Auger Observatory is an UHE Cosmic Ray detector
located in the Mendoza Province in Argentina. It consists of
an array of Water Cherenkov detectors spread over a total surface
of 3000 km^2 arranged in a triangular grid of 1.5 km side as well
as Fluorescence telescopes and other systems
(see 10.1016/j.nima.2015.06.058 for more information).
For neutrino searches from GW events with Auger, please refer to:
https://journals.aps.org/prd/pdf/10.1103/PhysRevD.94.122007

Alan M. Watson (UNAM), Nat Butler (ASU), Eleonora Troja (GSFC/UMD), Rosa
L. Becerra (UNAM), Simone Dichiara (UMD), Diego Gonz��lez (UNAM),
Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Margarita Pereyra
(UNAM), and Tanner Wolfram (ASU) report:

We observed 128 galaxies selected from the NED/CLU list with the COATLI
50-cm telescope and interim imager at the Observatorio Astron��mico
Nacional on the Sierra de San Pedro M��rtir
(http://coatli.astroscu.unam.mx) on the night of 2019-04-26 UTC. For
each galaxy, we typically obtained 150 seconds of exposure in the w
filter. Our observations are listed below. Analysis is proceeding.

We thank the COATLI technical team and the staff of the Observatorio
Astron��mico Nacional.

Start (UTC)       RA and Dec (J2000)  Galaxy
2019-04-26 03:44  182.7630  +25.5168  2MASX J12110307+2530599
2019-04-26 03:47  188.3071  +27.5841  IC 3494
2019-04-26 03:51  182.1638  +25.1281  2MASX J12083929+2507410
2019-04-26 03:54  179.3352  +22.1624  KUG 1154+224
2019-04-26 03:57  180.7254  +21.6448  KUG 1200+219
2019-04-26 04:01  184.5085  +26.0806  2MASX J12180207+2604500
2019-04-26 04:04  183.0157  +25.1190  2MASX J12120382+2507083
2019-04-26 04:10  184.8021  +25.7150  IC 3146
2019-04-26 04:14  189.6138  +28.4801  2MASX J12382707+2828478
2019-04-26 04:17  180.9844  +22.9801  KUG 1201+232
2019-04-26 04:21  185.6653  +27.7470  IC 3230
2019-04-26 04:24  182.7263  +25.2528  2MASX J12105427+2515102
2019-04-26 04:28  181.7513  +22.3879  2MASX J12070031+2223161
2019-04-26 04:31  187.8534  +26.7961  IC 3450
2019-04-26 04:34  184.4882  +25.0765  IC 3116
2019-04-26 04:38  185.9519  +27.7463  KUG 1221+280
2019-04-26 04:44  184.2770  +27.1926  2MASX J12170644+2711335
2019-04-26 04:48  185.9275  +26.8490  2MASX J12234260+2650561
2019-04-26 04:51  182.0900  +25.1909  2MASX J12082161+2511270
2019-04-26 04:55  184.8714  +25.8987  2MFGC 09705
2019-04-26 04:58  181.7447  +23.7051  2MASX J12065874+2342181
2019-04-26 05:01  190.7657  +30.3821  UGC 07891 NED01
2019-04-26 05:05  184.7850  +27.7624  2MASX J12190846+2745445
2019-04-26 05:08  182.9698  +25.4431  2MASX J12115275+2526352
2019-04-26 05:12  183.4407  +24.3560  2MASX J12134575+2421221
2019-04-26 05:18  241.3745  +24.2049  2MASX J16052994+2412169
2019-04-26 05:22  182.0299  +24.7903  2MASX J12080724+2447251
2019-04-26 05:25  185.1572  +26.1654  IC 3179
2019-04-26 05:29  192.7138  +31.0401  2MASX J12505128+3102236
2019-04-26 05:32  241.3353  +23.4874  2MASX J16052050+2329146
2019-04-26 05:36  186.2935  +25.8798  IC 3302
2019-04-26 05:39  242.8368  +22.4738  2MASX J16112110+2228253
2019-04-26 05:43  241.3670  +24.5229  2MASX J16052806+2431229
2019-04-26 05:46  179.5618  +21.8999  2MASX J11581481+2153594
2019-04-26 05:53  184.5249  +25.7112  2MASX J12180594+2542400
2019-04-26 05:57  178.7066  +22.1030  2MASX J11544958+2206106
2019-04-26 06:00  244.6924  +20.6921  2MASX J16184613+2041328
2019-04-26 06:04  186.4548  +26.7399  IC 3324
2019-04-26 06:07  188.9389  +30.0242  KUG 1233+302
2019-04-26 06:11  182.9716  +23.6437  2MASX J12115318+2338367
2019-04-26 06:14  236.4804  +26.9093  2MASX J15455527+2654333
2019-04-26 06:18  186.9607  +27.3807  2MASX J12275054+2722501
2019-04-26 06:22  187.9328  +26.8002  2MASX J12314393+2648008
2019-04-26 06:28  182.0403  +24.6768  2MASX J12080965+2440361
2019-04-26 06:31  245.7873  +20.0828  2MASX J16230893+2004582
2019-04-26 06:35  241.1113  +23.2575  2MASX J16042675+2315274
2019-04-26 06:38  244.4020  +20.8208  2MFGC 13087
2019-04-26 06:42  247.2044  +18.6858  2MASX J16284905+1841099
2019-04-26 06:45  188.2076  +28.9588  KUG 1230+292
2019-04-26 06:49  235.1367  +28.4220  2MASX J15403284+2825188
2019-04-26 06:53  244.5403  +21.5603  UGC 10321 NED04
2019-04-26 06:56  191.6240  +30.8486  2MASX J12462976+3050546
2019-04-26 07:02  184.7725  +27.2984  IC 3143
2019-04-26 07:06  241.1352  +23.9445  2MASX J16043249+2356393
2019-04-26 07:10  236.0194  +27.3464  2MASX J15440461+2720469
2019-04-26 07:13  182.1232  +25.2656  2MASX J12082949+2515560
2019-04-26 07:17  241.2167  +23.9408  2MASX J16045203+2356273
2019-04-26 07:20  185.7417  +28.4942  IC 3237
2019-04-26 07:24  243.1217  +22.6119  KUG 1610+227B
2019-04-26 07:28  234.3185  +29.9945  2MASX J15371644+2959397
2019-04-26 07:31  241.2392  +23.9076  2MASX J16045743+2354283
2019-04-26 07:37  232.4939  +30.9282  2MASX J15295860+3055425
2019-04-26 07:41  185.4638  +26.3636  IC 3206
2019-04-26 07:45  235.3756  +28.0977  2MASX J15413013+2805513
2019-04-26 07:48  242.5618  +22.2798  2MASX J16101484+2216471
2019-04-26 07:52  245.0006  +19.4868  2MASX J16200013+1929127
2019-04-26 07:55  244.5148  +19.8472  2MASX J16180359+1950499
2019-04-26 07:58  253.7886  -17.9404  2MASX J16550925-1756257
2019-04-26 08:02  183.6096  +24.1821  KUG 1211+244
2019-04-26 08:05  184.6317  +25.9993  2MASX J12183158+2559571
2019-04-26 08:12  244.9722  +18.8760  2MASX J16195329+1852337
2019-04-26 08:16  241.1951  +23.8051  2MASX J16044680+2348183
2019-04-26 08:19  186.7865  +28.9565  2MASX J12270877+2857229
2019-04-26 08:23  245.0050  +18.6073  2MASX J16200111+1836237
2019-04-26 08:27  244.4856  +19.1178  2MASX J16175654+1907039
2019-04-26 08:30  185.2458  +27.2876  2MASX J12205898+2717154
2019-04-26 08:34  183.4763  +25.1692  2MASX J12135424+2510091
2019-04-26 08:37  239.1263  +25.3290  2MASX J15563034+2519448
2019-04-26 08:41  240.9191  +24.9486  2MASX J16034054+2456555
2019-04-26 08:47  251.9904  -20.0771  2MASX J16475772-2004373
2019-04-26 08:51  244.6620  +19.1521  2MASX J16183883+1909079
2019-04-26 08:55  185.1663  +28.1220  2MASX J12203984+2807194
2019-04-26 08:58  242.6162  +23.7723  2MASX J16102788+2346201
2019-04-26 09:02  241.7240  +24.1507  2MASX J16065382+2409027
2019-04-26 09:05  244.5221  +21.5537  UGC 10321 NED01
2019-04-26 09:09  253.0308  -15.9408  2MASX J16520737-1556265
2019-04-26 09:12  245.5712  +18.6024  2MASX J16221705+1836088
2019-04-26 09:16  182.5894  +23.8117  2MASX J12102139+2348420
2019-04-26 09:22  248.6837  +17.1136  2MASX J16344407+1706482
2019-04-26 09:26  236.7935  +27.1077  2MASX J15471040+2706272
2019-04-26 09:29  247.7353  +16.5853  2MASX J16305646+1635074
2019-04-26 09:33  245.0037  +20.5053  2MASX J16200084+2030197
2019-04-26 09:36  241.1232  +24.1090  2MASX J16042959+2406323
2019-04-26 09:40  241.4533  +23.1037  2MASX J16054876+2306129
2019-04-26 09:44  252.6809  -17.3801  2MASX J16504342-1722483
2019-04-26 09:47  183.1095  +23.7284  2MASX J12122629+2343419
2019-04-26 09:51  244.5343  +20.9436  2MASX J16180824+2056369
2019-04-26 09:57  235.7265  +27.5767  2MASX J15425435+2734358
2019-04-26 10:01  242.2285  +24.3562  2MASX J16085484+2421220
2019-04-26 10:04  252.5841  -21.0833  2MASX J16502017-2105001
2019-04-26 10:08  244.0556  +20.4554  2MASX J16161336+2027191
2019-04-26 10:11  241.9449  +23.7905  2MASX J16074677+2347255
2019-04-26 10:15  234.6810  +29.4141  CGCG 166-023
2019-04-26 10:18  249.1245  +13.1593  2MASX J16362986+1309332
2019-04-26 10:22  241.2317  +23.9696  2MASX J16045560+2358113
2019-04-26 10:25  230.5441  +30.9400  2MASX J15221058+3056237
2019-04-26 10:31  240.5220  +25.7878  KUG 1559+259
2019-04-26 10:35  242.8522  +23.6745  2MASX J16112451+2340283
2019-04-26 10:38  245.7546  +20.4355  2MASX J16230105+2026072
2019-04-26 10:41  233.7091  +28.9272  2MASX J15345021+2855384
2019-04-26 10:45  248.9189  +13.1333  2MASX J16354056+1308003
2019-04-26 10:48  254.2265  -18.1893  2MASX J16565436-1811214
2019-04-26 10:52  245.1669  +18.8472  2MASX J16204007+1850497
2019-04-26 10:55  235.3256  +27.9190  2MASX J15411814+2755082
2019-04-26 10:59  238.8562  +25.5697  2MASX J15552546+2534107
2019-04-26 11:05  239.9639  +25.9146  2MASX J15595132+2554523
2019-04-26 11:09  235.4278  +28.0710  2MASX J15414267+2804162
2019-04-26 11:12  248.3433  +17.3044  2MASX J16332237+1718164
2019-04-26 11:15  235.3359  +27.7731  2MASX J15412065+2746242
2019-04-26 11:19  243.5524  +22.7777  2MASX J16141252+2246395
2019-04-26 11:22  239.2183  +24.9500  2MASX J15565239+2456597
2019-04-26 11:26  240.3571  +24.9833  KUG 1559+251
2019-04-26 11:29  241.2147  +23.9374  2MASX J16045152+2356153
2019-04-26 11:32  255.6592  -12.5202  2MASX J17023817-1231128
2019-04-26 11:39  241.8520  +22.5767  2MASX J16072447+2234356
2019-04-26 11:42  242.3100  +23.3823  2MASX J16091442+2322557
2019-04-26 11:46  235.2531  +28.3231  2MASX J15410076+2819224
2019-04-26 11:49  239.1760  +25.4779  2MASX J15564230+2528406

Nat Butler (ASU), Alan M. Watson (UNAM), Eleonora Troja (GSFC/UMD), Rosa
L. Becerra (UNAM), Simone Dichiara (UMD), Diego Gonz��lez (UNAM),
Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Margarita Pereyra
(UNAM), and Tanner Wolfram (ASU) report:

We observed 23 galaxies selected from the NED/CLU list with the
Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on
the 1.5m Harold Johnson Telescope at the Observatorio Astron��mico
Nacional on Sierra San Pedro M��rtir on the night of 2019-04-26 UTC. For
each galaxy, we typically obtained 720 seconds of exposure in g and i filters
and 540 seconds of exposure in Y and H filters. Our observations are listed
below. Analysis is proceeding.

We thank the staff of the Observatorio Astron��mico Nacional in San Pedro
M��rtir.

Start (UTC)       RA and Dec (J2000)    Galaxy
2019-04-26 03:41  182.76301  +25.51679  2MASX J12110307+2530599
2019-04-26 04:01  188.30713  +27.58410  IC 3494
2019-04-26 04:17  182.16379  +25.12808  2MASX J12083929+2507410
2019-04-26 04:48  179.33521  +22.16242  KUG 1154+224
2019-04-26 05:06  180.72538  +21.64475  KUG 1200+219
2019-04-26 05:25  184.50847  +26.08058  2MASX J12180207+2604500
2019-04-26 05:43  183.01570  +25.11901  2MASX J12120382+2507083
2019-04-26 06:09  184.80208  +25.71502  IC 3146
2019-04-26 06:32  189.61375  +28.48008  2MASX J12382707+2828478
2019-04-26 06:52  180.98436  +22.98009  KUG 1201+232
2019-04-26 07:24  185.66534  +27.74699  IC 3230
2019-04-26 07:42  182.72627  +25.25279  2MASX J12105427+2515102
2019-04-26 08:03  181.75129  +22.38786  2MASX J12070031+2223161
2019-04-26 08:22  187.85341  +26.79614  IC 3450
2019-04-26 08:51  184.48819  +25.07652  IC 3116
2019-04-26 09:08  185.95186  +27.74630  KUG 1221+280
2019-04-26 09:25  184.27696  +27.19256  2MASX J12170644+2711335
2019-04-26 09:45  185.92750  +26.84897  2MASX J12234260+2650561
2019-04-26 10:11  184.87139  +25.89869  2MFGC9705
2019-04-26 10:30  190.76567  +30.38206  UGC 07891 NED01
2019-04-26 10:49  241.37454  +24.20486  2MASX J16052994+2412169
2019-04-26 11:08  241.33534  +23.48742  2MASX J16052050+2329146
2019-04-26 11:40  242.83681  +22.47378  2MASX J16112110+2228253

Tianrui Sun,Jian Chen,Lei Hu,Fan Li, Ye Yuan, Yanning Fu, Yue Chen., Xuefeng Wu,Kelai Meng(PMO), Wen-xiong Li, Xinghan Zhang,Xiao-feng Wang(THU), Lifan Wang(PMO and TAMU)

We report the observations of the BAYESTAR skymap with GLADE catalogue of the BNS event S190425z,
(The LIGO Scientific Collaboration and the Virgo Collaboration, GCN 24168
Loading...
 
 ) with the Yaoan High Precision Telescope at Yaoan Observation Station(in Yunnan Province, China(101.1811�� E,25.528��N)), Purple Mountain Observatory.
We obtained images of ZTF19aarzaod and ZTF19aarykkb (Kasliwal et al., GCN 24191
Loading...
 
 ) in Rc band with exposure time 300s and calibrated to the PPMX catalogue. We performed image subtraction with template from PS1 r band images.

Object  ObserveTime  Band  Mag(Magerr) 
ZTF19aarykkb| 2019-04-25T19:10:32  |Rc  | 18.33(0.08)
ZTF19aarykkb| 2019-04-25T19:15:47  |Rc  | 18.33(0.08)
ZTF19aarykkb| 2019-04-25T19:21:03  |Rc  | 18.00(0.12)
ZTF19aarykkb| 2019-04-25T19:26:18  |Rc  | 18.39(0.09)
ZTF19aarykkb| 2019-04-25T19:31:34  |Rc  | 18.29(0.08)
ZTF19aarykkb| 2019-04-25T20:12:02  |Rc  | 18.28(0.08)
ZTF19aarykkb| 2019-04-25T20:33:53  |Rc  | 18.35(0.08)
ZTF19aarykkb| 2019-04-25T21:06:48  |Rc  | 18.15(0.14)
ZTF19aarykkb| 2019-04-25T21:17:44  |Rc  | 18.04(0.12)
ZTF19aarykkb| 2019-04-25T21:28:46  |Rc  | 18.09(0.11)
ZTF19aarykkb| 2019-04-25T21:39:43  |Rc  | 18.00(0.12)
ZTF19aarykkb| 2019-04-25T21:50:34  |Rc  | 18.04(0.12)
Object  ObserveTime  Band Type  Mag(Magerr)
ZTF19aarzaod| 2019-04-25T19:47:31  |Rc |Mag Subtract | 18.98(0.59)
ZTF19aarzaod| 2019-04-25T21:34:10  |Rc |Mag Limit | 18.87(0.51)
ZTF19aarzaod| 2019-04-25T19:42:15  |Rc |Mag Limit | 18.97(0.40)
ZTF19aarzaod| 2019-04-25T21:45:01  |Rc |Mag Limit | 18.88(0.52)
ZTF19aarzaod| 2019-04-25T20:50:21  |Rc |Mag Subtract | 18.92(0.56)
ZTF19aarzaod| 2019-04-25T20:39:21  |Rc |Mag Limit | 18.98(0.52)
ZTF19aarzaod| 2019-04-25T20:28:20  |Rc |Mag Subtract | 18.96(0.60)
ZTF19aarzaod| 2019-04-25T21:01:16  |Rc |Mag Subtract | 18.88(0.52)
ZTF19aarzaod| 2019-04-25T21:23:13  |Rc |Mag Subtract | 18.91(0.61)
ZTF19aarzaod| 2019-04-25T21:12:12  |Rc |Mag Limit | 18.93(0.57)
ZTF19aarzaod| 2019-04-25T19:37:00  |Rc |Mag Limit | 18.99(0.55)

J. Jencson (Caltech), K. De (Caltech), S. Anand (Caltech), M. M.
Kasliwal (Caltech), I. Andreoni (Caltech), T. Ahumada (UMD), D. A.
Perley (LJMU) report on behalf of the ZTF and GROWTH collaborations

We obtained near-IR spectroscopy of AT2019ebq
Loading...
 
  (GCN #24210
Loading...
 
 ) with the
Near-Infrared Echellette Spectrometer (NIRES) on the Keck II Telescope
on Mauna Kea. The spectrum shows broad P Cygni supernova-like features
including He I (10830 A) with a velocity of approx. 14000 km/s,
suggesting that this is a Type Ib/IIb supernova. Thus, this object is
unrelated to LIGO/Virgo S190425z (GCN #24168
Loading...
 
 ).

We thank the staff of Keck observatory, especially Percy Gomez and
Julie Renaud-Kim, and the observer, Wanqiu He, for facilitating this
Target of Opportunity observation.

LIGO/Virgo S190425z: Nearby Galaxies in the Updated Localization Volume

David O. Cook (Caltech/IPAC), Angela Van Sistine (UW Milwaukee), Leo Singer (NASA/GSFC), Igor Andreoni (Caltech), Michael Coughlin (Caltech), Bob Aloisi (UW Milwaukee), Patrick R. Brady (UW Milwaukee), Rick Ebert (Caltech/IPAC), George Helou (Caltech/IPAC), David Kaplan (UW Milwaukee), Mansi M. Kasliwal (Caltech), Joseph M. Mazzarella (Caltech/IPAC), and Marion Schmitz (Caltech/IPAC)

On behalf of the Global Relay of Observatories Watching Transients Happen (GROWTH) collaboration and the NASA/IPAC Extragalactic Database (NED) Team.

We spatially cross-matched the LIGO/Virgo S190425z (2-Update) trigger sky localization (90% containment volume) with the Census of the Local Universe (CLU; Cook et al. 2017; arxiv:1710.05016) galaxy catalog and found 56562 galaxies within the volume. The CLU catalog is a compilation of galaxies with existing redshifts from many sources (e.g., NED, SDSS, etc) and new galaxies from a 3PI steradian narrow-band survey to look for redshifted Halpha emission out to 200 Mpc with the Palomar Oschin 48-inch telescope (Cook et al. 2017; arxiv:1710.05016). We list here the top 20 CLU-matched galaxies sorted by stellar mass (Mstar) whose location on the sky and distance falls in the 90% volume reported by the BAYESTAR probability sky map (Singer et al. 2016). We also list the dust-corrected star formation rates (SFRs) for galaxies with GALEX FUV detections (a 'nan' for those with no detection).

For a more complete/extended list of galaxies in the 90% volume go to the NED Gravitational Wave Followup service at https://ned.ipac.caltech.edu/uri/NED::GWF/. This service provides downloadable galaxy lists and visualizations for candidate host galaxies. For each GW alert, these products are automatically generated and made available within minutes to expedite efficient electromagnetic followup observations. The NED top 20 list is sorted by 2MASS absolute K-band magnitude, but users can sort the entire list on a variety of other criteria (probability density, UV magnitudes, etc) after download.


          name              ra      dec   distmpc logsfr_fuv logmstar  dP_dV
------------------------ -------- ------- ------- ---------- -------- --------
         HIPASS J0029-15   7.3096 -15.0669   84.71        nan    13.25 3.03e-08
          HIZOA J1822-21 275.5775 -21.1603  105.49        nan    12.52 1.02e-07
SDSS J125614.10+565225.3 194.0588  56.8737  170.72        nan    12.50 2.65e-08
  2MASXi J0215532-232855  33.9721 -23.4821  155.60        nan    12.15 1.20e-07
 2MASX J06090714+2150343  92.2798  21.8428   92.75        nan    12.14 1.37e-07
 2MASX J05210136-2521450  80.2558 -25.3626  177.23       2.36    12.03 1.69e-07
            FAIRALL 0009  20.9407 -58.8058  195.77       1.83    11.95 5.60e-08
               LDCE 1285 271.5879 -25.4325  104.81        nan    11.92 3.44e-08
        IRAS  05223+1908  81.3187  19.1794  123.16        nan    11.87 1.01e-07
          ESO 250-G  012  63.2014 -46.6193  136.77       0.72    11.85 2.35e-07
                 ARK 120  79.0476  -0.1498  138.25        nan    11.83 2.01e-07
 2MASX J04444356-4433487  71.1814 -44.5635  195.96        nan    11.80 4.98e-07
 2MASX J17013663-2523008 255.4027 -25.3837  168.78        nan    11.79 3.41e-08
 2MASS J17421439-0843195 265.5582  -8.7228   95.94        nan    11.71 4.74e-08
                NGC 5995 237.1040 -13.7578  104.91       1.42    11.61 4.19e-08
            CGCG 049-037 227.9241   4.4919  155.60      -0.73    11.51 2.52e-08
                MRK 0486 234.1598  54.5592  193.00        nan    11.50 2.86e-08
   LCRS B034324.7-394349  56.3022 -39.5748  178.14       1.09    11.47 3.70e-07
            CGCG 219-058 213.2671  42.0054  170.39       0.18    11.47 9.93e-08
 2MASS J17415525-1211566 265.4803 -12.1991  154.06        nan    11.45 3.03e-08



Table: Top 20 galaxies in CLU that fall in the 90% probability volume for S190425z (2-Update) sorted by stellar mass. Column descriptions are as follows. name: galaxy name. ra: RA (J2000, decimal degrees). dec: Dec (J2000, decimal degrees). distmpc: galaxy distance (Mpc). logsfr_fuv: log10 of the star formation rate (SFR, Msun per year), derived from GALEX All Sky Kron FUV magnitudes via the prescription of Murphy et al. (2011), corrected for internal dust extinction using a combination of GALEX FUV and 22um ALLWISE fluxes (Hao et al. 2011). logmstar: log10 of the galaxy stellar mass (Msun), estimated from 3.4um ALLWISE fluxes and a mass-to-light ratio of 0.5 (McGaugh & Schombert et al. 2015).

Morokuma, T. (U. of Tokyo), Ohta, K. (Kyoto U.),
Yoshida, M., Aoki, K. (NAOJ/Subaru), Tanaka, M. (Tohoku U.),
Sasada, M., Nakaoka, T., Akitaya, H., Kawabata, K. S. (Hiroshima U.),
Itoh, R. (Bisei Astronomical Observatory), Utsumi, Y. (Stanford U./SLAC),
on behalf of J-GEM collaboration

We performed spectroscopic observations of AT2019ebq
Loading...
 
 /PS19qp (Smith et 
al. 2019, GCN, 24210), a possible counterpart to the gravitational wave 
event S190425z, with the Faint Object Camera and Spectrograph (FOCAS; 
Kashikawa et al. 2002, PASJ, 54, 819) on the 8.2-m Subaru Telescope. We 
started our observations at UT 2019-04-26 13:43, about 1.2 days after 
the event.

We took a red part of optical spectrum, covering from 7,000 A to 10,000 
A. At the redshift of z=0.037 (Nicholl et al. 2019, GCN, 24217; Jonker 
et al. 2019, GCN, 24221), the spectrum shows a broad P-Cygni profile 
with an absorption minimum around 8200 A and an emission peak around 
8600 A. There is also another absorption feature around 7500 A. These 
features can be attributed to the Ca II IR triplet and the O I 7774, 
respectively. Therefore, this source is likely to be a reddened 
supernova and unlikely to be associated with the gravitational wave event.

P. Schady (U.Bath), T.-W. Chen (MPE, Humboldt Fellow), T. Schweyer (MPE), D. B. Malesani (DAWN/NBI and DARK/NBI) and J. Bolmer (MPE) report:

We observed the field of the AT2019ebq
Loading...
 
 /PS19qp (Smith et al., GCN #24210
Loading...
 
 ; Nicholl et al., GCN #24217
Loading...
 
 ; Jonker et al., GCN #24221
Loading...
 
 ) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La Silla Observatory (Chile). 

Observations started at 09:08 UT on 26 of April 2019, about 1.04 days after the GW S190425z detection (LIGO and Virgo Collaboration, GCN #24168
Loading...
 
 ), and were performed under seeing conditions of 1���.4, and at an average airmass of 1.3. We detect the candidate and based on 25 min of total exposure time in optical and 26 min in NIR, we derive the following preliminary magnitudes (all in the AB system):

r = 20.78 +/- 0.20 mag, 
i = 20.00 +/- 0.15 mag, and
z = 19.60 +/- 0.15 mag.

The magnitudes are measured using aperture photometry with a small aperture size of 0".75. We caution that the object is blended with the galaxy nucleus, and that the removal of the variable and bright host background may introduce further systematic errors.

Given magnitudes are calibrated against Pan-STARRS field stars and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V) = 0.51 mag in the direction of the counterpart (Schlafly & Finkbeiner 2011). 

We acknowledge excellent help in obtaining these data from the observer Jose Ignacio Vines and supporting astronomer Angela Hempel on La Silla.

The LIGO Scientific Collaboration and the Virgo Collaboration report:

We have re-analyzed LIGO data around the time of the compact binary
coalescence (CBC) candidate S190425z (GCN 24168
Loading...
 
 ). Parameter
estimation has been performed using LALInference [1] and a new sky
map, LALInference.fits.gz, is available for retrieval from the
GraceDB event page:

https://gracedb.ligo.org/superevents/S190425z

For the LALInference.fits.gz skymap, the 90% credible region is 7461
deg2. Marginalized over the whole sky, the a posteriori luminosity
distance estimate is 156 +/- 41 Mpc (a posteriori mean +/- standard
deviation). This is the preferred sky map at this time.

For further information about analysis methodology and the contents
of this alert, refer to the LIGO/Virgo Public Alerts User Guide
<https://emfollow.docs.ligo.org/userguide/>.

 [1] Veitch et al. PRD 91, 042003 (2015)

M. Blazek (HETH/IAA-CSIC), N. Christensen (Artemis),
E. Howell (OzGrav-UWA), M. Vardosanidze (Iliauni), M. Boer (Artemis),
L. Eymar (Artemis), A. Klotz (IRAP), R. Laugier (Artemis),
K. Noysena (Artemis, IRAP), S. Antier (APC), S. Basa (LAM),
D. Corre (LAL), M. Coughlin (Caltech), D. Coward (OzGrav-UWA),
J.G. Ducoin (LAL), B. Gendre (OzGrav-UWA), P. Hello (LAL),
C. Lachaud (APC), N. Leroy (LAL), D. Turpin (NAOC), X. Wang (THU)

Report on behalf of the TAROT network and GRANDMA collaborations.

We performed tiled observations of LIGO/VIRGO event S190425z (GCN #24168
Loading...
 
 )
with the TAROT-Reunion (Les Makes Observatory, La R��union Island, France)
telescope operating in clear filter.

The observation started on 04/25/19 14:56:19 UTC which corresponds
approximately to 6.65 hours after the GW trigger time.

We performed the following tiled observations :

+------------+------------+---------+---------+---------+
| TStart     | TEnd       | RA      | DEC     |   Proba |
| [UTC]      | [UTC]      | [deg]   | [deg]   |     [%] |
|------------+------------+---------+---------+---------|
| 2019-04-25 | 2019-04-25 | 194.595 | 30      |     0.2 |
| 14:56:19   | 22:29:56   |         |         |         |
| 2019-04-25 | 2019-04-25 | 182.338 | 25.714  |     0.2 |
| 17:03:57   | 17:55:18   |         |         |         |
| 2019-04-25 | 2019-04-25 | 189.73  | 30      |     0.3 |
| 17:16:58   | 21:51:14   |         |         |         |
| 2019-04-25 | 2019-04-26 | 243.117 | 25.714  |     0.6 |
| 18:07:39   | 01:40:56   |         |         |         |
| 2019-04-25 | 2019-04-26 | 246.076 | 21.429  |     0.7 |
| 18:20:49   | 01:09:32   |         |         |         |
| 2019-04-25 | 2019-04-25 | 238.442 | 25.714  |     0.9 |
| 19:11:40   | 22:16:40   |         |         |         |
| 2019-04-25 | 2019-04-26 | 241.519 | 21.429  |     0.7 |
| 19:43:51   | 00:18:12   |         |         |         |
+------------+------------+---------+---------+---------+


The Probability refers to the 2D spatial probability of the GW skymap
enclosed in a given tile. Each tile is 4.2x4.2 degrees. These observations
cover about 3% of the cumulative probability of the skymap. The typical
3-sigma limiting magnitude for a two minutes exposure is 17 mag.

The coverage map is available at:
https://grandma-owncloud.lal.in2p3.fr/index.php/s/tZTxGSoCEMc4fwG

Optical transient candidates will be sent through another GCN
circular depending on our data analysis.

GRANDMA (Global Rapid Advanced Network Devoted to the Multi-messenger
Addicts) is a network of robotic telescopes connected all over the
world with both photometry and spectrometry capabilities for Time-
domain Astronomy (https://grandma.lal.in2p3.fr/). Details on the TAROT
telescopes are available on the GRANDMA web pages or on
http://tarot.obs-hp.fr/

L. Rhodes, R. Fender, D. Williams, J. Bright (Oxford), K. Mooley (NRAO, Caltech; Jansky Fellow), A Horesh (The Hebrew University of Jerusalem), Dave Green, David Titterington (MRAO) and the JAGWAR collaboration.

We observed the positions of the two reported GW190425z afterglow candidates from GCN 24191
Loading...
 
  with the AMI Large Array at 15GHz. We started observing the first candidate, ZTF19aarykkb, on 2019 April 26.04 for 3 hrs (0.70 days after the initial detection). The second transient reported, ZTF19aarzoad, was observed with AMI Large Array at 15GHz on 2019 April 26.17 for 3 hrs (0.82 days after the initial detection). Due to the size of the AMI beam, we are unable to spatially resolve either transient source from their respective proposed host galaxies. We acknowledge that these two sources have since been shown to be unrelated to the gravitational wave detection (GCNs 24204
Loading...
 
  & 24205).

Furthermore, we have scheduled an observation of the promising afterglow candidate: AT2019ebq
Loading...
 
  (GCN 24210
Loading...
 
 ).

We thank the MRAO staff for scheduling these observations.

Daichi Hiramatsu (LCO/UCSB), Craig Pellegrino (LCO/UCSB), Jamison Burke
(LCO/UCSB), D. Andrew Howell (LCO/UCSB), Iair Arcavi (Tel Aviv University),
Curtis McCully (LCO) on behalf of the Las Cumbres GW Follow-up Collaboration

We report 300s gri-band images of the following galaxies in the LIGO/Virgo
S190425z localization region (GCN 24168
Loading...
 
 ) with the Las Cumbres Observatory
1m telescopes at Sutherland, South Africa. We find no obvious candidates
after performing image subtraction using SDSS images as templates.

Name         RA(J2000) DEC(J200) Time(UT)           Filter Limmag

CSCG080-051 249.859940 +11.210459 2019-04-25 23:30:33 i 21.4

2MASXJ16542402-0953212 253.600113 -9.889244 2019-04-25 21:36:06 i 21.0

2MASXJ16542402-0953212 253.600113 -9.889244 2019-04-25 21:41:48 r 21.8

2MASXJ16542402-0953212 253.600113 -9.889244 2019-04-25 21:47:30 g 22.4

CSCG137-046 242.315292 +25.712521 2019-04-25 22:16:57 i 20.8

CSCG137-046 242.315292 +25.712521 2019-04-25 22:22:38 r 21.6

CSCG137-046 242.315292 +25.712521 2019-04-25 22:28:19 g 22.5

NGC4555      188.921585 +26.522999 2019-04-25 19:49:40 i 21.8

NGC4555      188.921585 +26.522999 2019-04-25 19:55:21 r 22.6

NGC4555      188.921585 +26.522999 2019-04-25 20:01:02 g 22.7

NGC4375      186.252045 +28.558516 2019-04-25 19:36:20 i 20.8

NGC4375      186.252045 +28.558516 2019-04-25 19:42:01 r 22.5

NGC4375      186.252045 +28.558516 2019-04-25 19:47:42 g 22.7

NGC4585      189.555481 +28.936903 2019-04-25 19:55:31 i 20.4

NGC4585      189.555481 +28.936903 2019-04-25 20:01:12 r 22.0

NGC4585      189.555481 +28.936903 2019-04-25 20:06:54 g 22.7

UGC10412     247.400574 +15.658440 2019-04-25 23:04:17 i 21.5

UGC10412     247.400574 +15.658440 2019-04-25 23:09:59 r 22.1

UGC10412     247.400574 +15.658440 2019-04-25 23:15:41 g 22.4

D.Steeghs(1), Lyman, J. (1), M.Dyer(3), D.Galloway(2), V.Dhillon(3),
P.O'Brien(4), G.Ramsay(5), D.Pollacco(1), E.Thrane(2),
S.Poshyachinda(6), E.Palle(7), K.Ulaczyk(1), R.Cutter(1),
A.Levan(1), T. Marsh(1), R.West(1), K.Wiersema(1), B.Gompertz(1),
E.Stanway(1), K.Ackley(2), A.Obradovic(2), Y-L.Mong(2), A.Casey(2),
M.Brown(2), E.Rol(2), J.Mullaney(3), S.Littlefair(3),
L.Makrygianni(3), E.Daw(3), J.Maund(3), R.Starling(4), R.Eyles(4),
U.Sawangwit(6), D.Mkrtichian(6), S.Awiphan(6),S.Aukkaravittayapun(6),
P.Irawati(6), M.Kennedy(8), R.Breton(8), D.Mata-Sanchez(8),
T.Heikkila(9), R.Kotak(9)
(1) Warwick University; (2) Monash University; (3) Univ. of Sheffield;
(4) University of Leicester; (5) Armagh Observatory;
(6) National Astronomical Research Institute of Thailand;
(7) Instituto de Astrofisica de Canarias; (8) Univ. of Manchester;
(9) University of Turku

report on behalf of the GOTO collaboration:

We report on optical observations with the Gravitational-wave Optical
Transient Observer in response to the BNS event S190425z (GCN #24168
Loading...
 
 ).

Targeted observations across 136 pointings containing 29.6% of the
source location probability across 2,134 sqr. degrees (based on the
initial BAYESTAR skymap) were performed between 20:38 UT Apr 25 and
05:33 UT Apr 26 2019.

Each pointing spans 4.9x3.7 square degrees and consisted of 3x60s
exposures in our L-band filter (400-700nm passband) with typical
5-sigma photometric depth of g=20.1, based on a photometric
calibration against PS1 sources. A coverage map is available at
http://goto-observatory.warwick.ac.uk/S190425z.html

Images are processed immediately after acquisition using the GOTOphoto
pipeline. Difference imaging was performed on the median of each
triplet of exposures using recent survey observations of the same
pointings. Source candidates were initially filtered using a
classifier and cross-matched against a variety of catalogs, including
the MPC and  PS1. Human candidate vetting was performed during data
acquisition and processing in case of notable detections.

We recover a number of known/already reported transients and variable
objects, but no new candidates were detected that could be credibly
associated with S190425z.

Our coverage includes some of the PS1 candidates (Smith et al. GCN
#24210
Loading...
 
 ), but we did not cover the position of AT2019ebq
Loading...
 
 /PS19qp, which
remains an object of interest (Jonker et al. GCN #24221
Loading...
 
  ; Coughlin et
al. GCN #24223
Loading...
 
 ).

We also reviewed the locations of the marginal ATLAS candidates
reported in McBrien et al. (GCN #24197
Loading...
 
 ), but detect no sources at
these locations, in line with Perley et al. (GCN #24202
Loading...
 
 ). The 5-sigma
limits are provided below.

Name       | IAU Name   | Obs. MJD | Image lim mag (L band 5sig)
ATLAS19hxm |  AT2019dzv
Loading...
 
  | 58598.96 | 20.08
ATLAS19hyx |  AT2019ebl
Loading...
 
  | 58599.03 | 20.63
ATLAS19hyo |  AT2019eao
Loading...
 
  | 58598.93 | 20.50
ATLAS19hwn |  AT2019ebm
Loading...
 
  | 58598.89 | 20.65
ATLAS19hwh |  AT2019ebn
Loading...
 
  | 58598.96 | 20.67


GOTO is operated at the La Palma observing facilities of the
University of Warwick on behalf of a consortium including the
University of Warwick, Monash University, Armagh Observatory, the
University of Leicester, the University of Sheffield, the National
Astronomical Research Institute of Thailand (NARIT) and the Instituto
de Astrofisica de Canarias (IAC) (https://goto-observatory.org/)

Authors: Michael W. Coughlin (Caltech), Shreya Anand (Caltech), Tomas
Ahumada (UMD)

On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of
Observatories Watching Transients Happen (GROWTH) collaborations

We have analyzed the list of objects reported in Smith et al. (24210),
and examined ZTF alerts for the same objects. We find that 7 of the
events listed below have recent, previous detections with ZTF prior to
the gravitational wave event trigger time and are likely unrelated to the
BNS event S190425z (The LIGO Scientific Collaboration and the Virgo
Collaboration, GCN 24168
Loading...
 
 ).

Name            PS Name    ZTF Name
AT2019ebu
Loading...
 
    PS19pp      ZTF19aasbgll
AT2019ebw
Loading...
 
   PS19pq      ZTF19aasazok
AT2019ecc
Loading...
 
    PS19pw      ZTF19aapwgpg
AT2019eck
Loading...
 
    PS19qe      ZTF19aapfrrw
AT2019ecl
Loading...
 
     PS19qg      ZTF19aasgwnp
AT2019ebr
Loading...
 
    PS19qj       ZTF18aaoxrvr
AT2019ebo
Loading...
 
    PS19qn     ZTF19aarpgau

ZTF and GROWTH are worldwide collaborations comprising Caltech, USA;
IPAC, USA, WIS, Israel; OKC, Sweden; JSI/UMd, USA; U Washington, USA;
DESY, Germany; MOST, Taiwan; UW Milwaukee, USA; LANL USA; TTU USA;
Tokyo Tech, Japan; IIT-B, India; IIA, India; LJMU, UK and USyd, Australia. ZTF
acknowledges the generous support of the NSF under AST MSIP Grant No
1440341. GROWTH acknowledges generous support of the NSF under PIRE
Grant No 1545949. Alert distribution service provided by DIRAC@UW
(Patterson et al. 2019). Alert filtering and follow-up co-ordination
is being undertaken by the GROWTH marshal system (Kasliwal et al.
2019).

-- 
Michael Coughlin

David and Ellen Lee Prize Postdoctoral Fellow
LIGO Laboratory
West Bridge, Rm. 257
California Institute of Technology
MC 100-36
Pasadena, CA 91125

email: mcoughli@ligo.caltech.edu
website: http://www.michaelwcoughlin.com
phone: +1 952 836 7113

C. League (LIU Brooklyn), M.J. Kavic (SUNY Old Westbury), J.H.
Simonetti (Virginia Tech), J. Dowell (U New Mexico), G.B. Taylor (U
New Mexico), J. Tsai, J. Kanner (Cal Tech), P. Shawhan (U Maryland),
C. Yancey (U Maryland)

The Long Wavelength Array (LWA1, located west of Socorro, New Mexico,
US) made beam-formed observations for 4 hours on April 25 following the
LVC_INITIAL notice S190425z (GCN 24168
Loading...
 
 ). Observations began at 09:02:43
UTC, about 2 minutes after the notice, which was ~45 minutes after the
detection.

The observations were centered at frequencies 25.85 MHz and 45.45 MHz,
each with a bandwidth of 19.6 MHz. The FWHM is 15.499 degrees at 25.85
MHz, and 6.648 degrees at 45.45 MHz.

The three beams were centered at RA 16.171h, Dec 22.831deg; RA
15.937h, Dec 26.110deg; RA 16.382h, Dec 19.313deg.

Data analysis is under way.

S.Dichiara (UMD, NASA-GSFC), P. Gatkine (UMD), J. Durbak (UMD),
E. Troja (UMD, NASA-GSFC), S.B. Cenko (NASA-GSFC), A. Kutyrev
(UMD, NASA-GSFC), S. Veilleux (UMD), report on behalf of a
larger collaboration:

We observed ZTF19aarykkb (Kasliwal et al., GCN 24191
Loading...
 
 ) using the the DeVeny
spectrograph mounted on the 4.3m Discovery Channel Telescope.
We obtained 22.5 min exposures at an average airmass of 1.5. Our spectra
cover
the wavelength range ~3,600-8,000 Angstrom.
A preliminary analysis our spectrum shows a bright emission line likely
associated to the H-alpha transition and a relatively featureless
continuum.
Overall our results are consistent with the reports from Pavana (GCN 24200
Loading...
 
 )
and
Perley (GCN 24204
Loading...
 
 ).

We thank the staff of the Discovery Channel Telescope in particular Andrew
Hayslip,
Ishara Nisley for assistance with these observations. We also thank
Jennifer Hanley
for contributing her time.

K. Morihana (Nagoya Univ.), M. Jian (Univ. of Tokyo), T. Nagayama (Kagoshima Univ.)
report on behalf of J-GEM collaboration:


We observed ZTF19aarykkb and ZTF19aarzaod reported by the Zwicky Transient Facility 
(Kasliwal et al., GCN 24191
Loading...
 
 ) with the near-infrared (J, H, Ks) simultaneous imaging camera SIRIUS 
attached to 1.4 m telescope IRSF (InfraRed Survey Facility) in Sutherland observatory, South Africa.

The observation started on 2019-04-26 00:19:13 UT. The exposure times in J-, H-, Ks-bands are
~30min (ZTF19aarykkb) and ~40 min (ZTF19aarzaod), respectively. We performed aperture photometry 
and the magnitude are listed below. The photometric magnitudes may have an effect from the host 
galaxy and nearest stars.

Target                              UTC                   J  (err)        H (err)         Ks (err) 
---------------------------------------------------------------------------------------------------
ZTF19aarykkb   2019-04-26 00:36:51.7   16.8 (0.1)  16.4 (0.1)    16.1 (0.1)  
ZTF19aarzaod   2019-04-26 01:25:52.9   17.4 (0.1)  16.7 (0.1)   16.4 (0.1) 
---------------------------------------------------------------------------------------------------

Given magnitudes were calibrated against 2MASS point sources (Vega System)  in the field.

Y. Shimizu (Kanagawa U),
A. Yoshida, T. Sakamoto, V. Pal'shin, S. Sugita (AGU),
Y. Kawakubo (LSU),K. Yamaoka (Nagoya U), S. Nakahira (RIKEN),
Y. Asaoka, S. Ozawa, S. Torii (Waseda U),
T. Tamura (Kanagawa U), N. Cannady, M. L. Cherry (LSU),
S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena)
and the CALET collaboration:

At the trigger time of the compact binary merger candidate S190425z,
T0=2019-04-25 08:18:05.017 UTC (The LIGO Scientific Collaboration and
Virgo Collaboration, GCN Circ. 24168
Loading...
 
 ), the high-voltage of the CALET
Gamma-ray Burst Monitor (CGBM) detectors were off
(from T0-192 sec to T0+1084 sec).

The CALET Calorimeter (CAL) was operating in high energy trigger mode
at the trigger time of S190425z. Using the CAL data, we have searched for
gamma-ray events in the 10-100 GeV band within the time interval
T0 +/- 60 sec and found no candidates.
The 90% upper limit of CAL is 1.0x10^-4 erg/cm2/s (10-100 GeV) when
the summed LIGO-Virgo probability reaches 5%.
The CAL FOV was centered at RA=131.3 deg, Dec=-43.6 deg at T0.

M. Nicholl, P. Short (Edinburgh), S. J. Smartt, K. W. Smith (QUB), K. Chambers, M. Huber (IfA) , J. Anderson (ESO), T.-W. Chen (MPE), C. Inserra (Cardiff), O. Yaron (Weizmann), D. R. Young (QUB), C. Angus, M. Pursiainen, P. Wiseman (Southampton), S. Taubenberger (MPA), M. Gromadzki (Warsaw) on behalf of the ePESSTO+ collaboration

We observed PS19qp (Smith et al., GCN 24210
Loading...
 
 ) a potential counterpart to the gravitational wave trigger S190425z (GCN 24168
Loading...
 
 ), under the advanced Public ESO Spectroscopic Survey for Transient Objects (ePESSTO+; see Smartt et al. 2015, A&A, 579, 40 http://www.pessto.org). The observations were performed on the ESO New Technology Telescope at La Silla with the EFOSC2 instrument.

The transient is coincident with a probable host galaxy 2MASS J17011849-0700102. Preliminary reduction of our NTT spectrum (1800s, Grism#13) shows a red and mostly featureless continuum, with a narrow H-alpha emission line, likely from the host galaxy, at z=0.037.

With this redshift and a foreground extinction of A_v = 1.3 mag (Schlafly & Finkbeiner 2011), the apparent magnitude of i=20.4 mag reported by Smith et al. corresponds to an absolute magnitude of -16.7. Further observations are in progress.

Joonho Kim (SNU), Myungshin Im (SNU), Chung-Uk Lee (KASI), Seung-Lee Kim
(KASI), Gregory S.H. Paek (SNU), Gu Lim (SNU), Sophia Kim (SNU), Sungyong
Hwang (SNU), Changsu Choi (SNU), Insu Paek (SNU), Suhyun Shin (SNU), Bomi
Park (SNU), Soojong Pak (KHU), Hyung Mok Lee (KASI), Hyun-Il Sung (KASI), on
behalf of a larger collaboration


We observed 120 host galaxy candidates in the 50% localization area of the BNS
merger candidate, S190425z, detected by LIGO/Virgo (GCN #24168
Loading...
 
 ) using the
KMTNet 1.6m telescopes at SSO, SAAO, and CTIO. The observation started at
2019-04-25 12:28 UT, and the images were taken in R-band with 120 sec
exposure time. No obvious transient has been identified. The list of
the targets
is given below.


16465757-1511349             16:48:57.00    -15:41:35.0

16483366-1520059             16:50:33.00    -15:50:06.0

17010310-1310184             17:03:03.00    -13:40:18.0

16372742-3044337             16:39:27.00    -31:14:34.0

16371371-2625123             16:39:13.00    -26:55:12.0

17033015-1301444             17:05:30.00    -13:31:44.0

17073219-1329173             17:09:32.00    -13:59:17.0

17432323-0325009             17:45:23.00    -03:55:01.0

16442971-2954301             16:46:29.00    -30:24:30.0

17404358-0608537             17:42:43.00    -06:38:54.0

17214929-0252202             17:23:49.00    -03:22:20.0

17042170-1300047             17:06:21.00    -13:30:05.0

16461237-0001563             16:48:12.00     00:31:56.0

17052059-1354058             17:07:20.00    -14:24:06.0

16551898-0715115             16:57:19.00    -07:45:12.0

16445871-0011441             16:46:58.00     00:41:44.0

17075556-0235287             17:09:55.00    -03:05:29.0

16365968-3055576             16:38:59.00    -31:25:58.0

17281431-0406583             17:30:14.00    -04:36:58.0

17343248-0659255             17:36:32.00    -07:29:26.0

16535846-2149010             16:55:58.00    -22:19:01.0

17081503-1333425             17:10:15.00    -14:03:43.0

16460002-1309243             16:48:00.00    -13:39:24.0

16350424-3054512             16:37:04.00    -31:24:51.0

16263236-3441507             16:28:32.00    -35:11:51.0

17222779-0505074             17:24:27.00    -05:35:07.0

16573248-2246391             16:59:32.00    -23:16:39.0

17030983-1247564             17:05:09.00    -13:17:56.0

17423503-0657581             17:44:35.00    -07:27:58.0

16473633-1509476             16:49:36.00    -15:39:48.0

16352839-2500426             16:37:28.00    -25:30:43.0

17161661-0811018             17:18:16.00    -08:41:02.0

17200620-0351381             17:22:06.00    -04:21:38.0

16512494-2254080             16:53:24.00    -23:24:08.0

16464891-0037544             16:48:48.00    -01:07:54.0

16452069-2037012             16:47:20.00    -21:07:01.0

16521781-2304586             16:54:17.00    -23:34:59.0

16495473-0636040             16:51:54.00    -07:06:04.0

17265688-0317354             17:28:56.00    -03:47:35.0

16471866-1456270             16:49:18.00    -15:26:27.0

17295066-0702448             17:31:50.00    -07:32:45.0

16532852-2312115             16:55:28.00    -23:42:12.0

16553496-0723587             16:57:35.00    -07:53:59.0

16435593-2529433             16:45:55.00    -25:59:43.0

17455093-0235298             17:47:50.00    -03:05:30.0

16563795-0712066             16:58:38.00    -07:42:07.0

04091988-5327483             04:11:19.00    -53:57:48.0

17073496-1637323             17:09:35.00    -17:07:32.0

17041344-1318227             17:06:13.00    -13:48:23.0

16440857-2854193             16:46:08.00    -29:24:19.0

16481805-1831303             16:50:18.00    -19:01:30.0

16545475-2329211             16:56:54.00    -23:59:21.0

17165559-0453060             17:18:55.00    -05:23:06.0

16502768+0005349             16:52:27.00     00:24:25.0

16550792-1801417             16:57:07.00    -18:31:42.0

16433259-2024343             16:45:32.00    -20:54:34.0

04171577-3858578             04:19:15.00    -39:28:58.0

16473469-2121514             16:49:34.00    -21:51:51.0

16301048-2822223             16:32:10.00    -28:52:22.0

17184030-0628489             17:20:40.00    -06:58:49.0

16480630-0037546             16:50:06.00    -01:07:55.0

17144035+0007545             17:16:40.00     00:22:05.0

04073433-5305504             04:09:34.00    -53:35:50.0

16482162-0407526             16:50:21.00    -04:37:53.0

17145452-1317481             17:16:54.00    -13:47:48.0

16472494-1813304             16:49:24.00    -18:43:30.0

16505041+0015538             16:52:50.00     00:14:06.0

16514833-1253444             16:53:48.00    -13:23:44.0

16553956-2238314             16:57:39.00    -23:08:31.0

16463548-2310136             16:48:35.00    -23:40:14.0

16595401-0445514             17:01:54.00    -05:15:51.0

16552065-0650095             16:57:20.00    -07:20:10.0

17235027-0820347             17:25:50.00    -08:50:35.0

17381357-0542425             17:40:13.00    -06:12:43.0

17475210-1053145             17:49:52.00    -11:23:15.0

17060471-1648304             17:08:04.00    -17:18:30.0

17465488-1053325             17:48:54.00    -11:23:33.0

17363676-0626500             17:38:36.00    -06:56:50.0

17420617-0926068             17:44:06.00    -09:56:07.0

16321778-3137378             16:34:17.00    -32:07:38.0

16501134-2227582             16:52:11.00    -22:57:58.0

16401811-2559083             16:42:18.00    -26:29:08.0

16305178-2811517             16:32:51.00    -28:41:52.0

16485650-2222422             16:50:56.00    -22:52:42.0

16461899-2105509             16:48:19.00    -21:35:51.0

17045066-1327563             17:06:50.00    -13:57:56.0

16500186-1754372             16:52:01.00    -18:24:37.0

16474585-2118434             16:49:45.00    -21:48:43.0

16480372-1159506             16:50:03.00    -12:29:51.0

04234351-3757099             04:25:43.00    -38:27:10.0

16402247-2211300             16:42:22.00    -22:41:30.0

16571736-1918597             16:59:17.00    -19:49:00.0

17080532-1638036             17:10:05.00    -17:08:04.0

17470574-0313407             17:49:05.00    -03:43:41.0

16501038-0833255             16:52:10.00    -09:03:26.0

17061698-0319254             17:08:17.00    -03:49:25.0

17012529-0757290             17:03:25.00    -08:27:29.0

16381154-3012590             16:40:11.00    -30:42:59.0

16435072-1829093             16:45:50.00    -18:59:09.0

17084763-1142374             17:10:47.00    -12:12:37.0

17275586-0352269             17:29:55.00    -04:22:27.0

16313752-2805243             16:33:37.00    -28:35:24.0

17211157-0330159             17:23:11.00    -04:00:16.0

17193554-0510154             17:21:35.00    -05:40:15.0

17282222-0311222             17:30:22.00    -03:41:22.0

16521779-1513294             16:54:17.00    -15:43:29.0

16433655-1750124             16:45:36.00    -18:20:12.0

16334229-3259350             16:35:42.00    -33:29:35.0

16392252-2303588             16:41:22.00    -23:33:59.0

17181392-0019465             17:20:13.00     00:49:47.0

17102195-0424569             17:12:22.00    -04:54:57.0

16522199-0744343             16:54:22.00    -08:14:34.0

17243739-0506362             17:26:37.00    -05:36:36.0

04005870-5341349             04:02:58.00    -54:11:35.0

16504578-2224476             16:52:45.00    -22:54:48.0

16280047-3312041             16:30:00.00    -33:42:04.0

16492033-1525363             16:51:20.00    -15:55:36.0

17453210-0452328             17:47:32.00    -05:22:33.0

17151656-1310140             17:17:16.00    -13:40:14.0

16554312-0420465             16:57:43.00    -04:50:47.0


-- 

--
Joonho Kim
joonho@astro.snu.ac.kr
Graduate Student,
Astronomy Program, Dept. of Physics & Astronomy,
Seoul National University, Seoul, Korea

���

P. Short, M. Nicholl (Edinburgh), S. J. Smartt, K. W. Smith (QUB), K. Chambers, M. Huber (IfA) , J. Anderson (ESO), T.-W. Chen (MPE), C. Inserra (Cardiff), O. Yaron (Weizmann), D. R. Young (QUB), C. Angus, M. Pursiainen, P. Wiseman (Southampton), S. Taubenberger (MPA), M. Gromadzki (Warsaw) on behalf of the ePESSTO+ collaboration

We observed PS19qo (Smith et al., GCN 24210
Loading...
 
 ) a potential counterpart to the gravitational wave trigger S190425z (GCN 24168
Loading...
 
 ), under the advanced Public ESO Spectroscopic Survey for Transient Objects (ePESSTO+; see Smartt et al. 2015, A&A, 579, 40 http://www.pessto.org). The observations were performed on the ESO New Technology Telescope at La Silla with the EFOSC2 instrument.

This candidate was chosen because of its apparent association with a cataloged galaxy at 199 Mpc. The NTT spectrum gives a good match to normal Type II SN at z=0.057.

A. J. Castro-Tirado, Y.-D. Hu, X.-Y. Li, E. Fernandez-Garcia and V. 
Casanova (IAA-CSIC), A. F. Valeev and V. V. Sokolov (SAO-RAS), I. 
Carrasco, A. Castellon and C. Perez del Pulgar (UMA), M. D. 
Caballero-Garcia (ASU-CAS), S. B. Pandey (ARIES) and N. Castro-Rodriguez 
(GRANTECAN, IAC, ULL), on behalf of a larger collaboration, report:

Following the report of the new transient ZTF19aarzaod (Kasliwal et al., 
GCN 24191
Loading...
 
 ) for the GW event S190425z (GCN 24168
Loading...
 
 ), we observed the target 
with the 1.5m telescope at the Observatorio de Sierra Nevada (Spain), 
measuring a R-band mag of 20.5 on Apr 26, 01:48 UT. An optical spectrum 
(600s) covering the range 3700-7500 A was obtained with the 10.4m GTC 
telescope equipped with OSIRIS in La Palma (Spain) on Apr 26, 03:40 UT. 
It shows a red continuum with a broad emission consistent with being 
H-alpha at the redshift of the host galaxy (z=0.0279) besides a narrow 
H-beta emission line at a consistent redshift. Therefore we rule out the 
relationship of ZTF19aarzaod to the GW event S190425z in agreement with 
Buckley et al. (GCN 24205
Loading...
 
 ), Izzo et al. (GCN 24208
Loading...
 
 ), Wiersema (GCN 
24209
Loading...
 
 ) and Nicholl et al. (GCN 24211
Loading...
 
 ).

We acknowledge the excellent support from the GTC staff.

S. Xiao, Q. Luo, C. Cai, Q.B.Yi, C. K. Li, X. B. Li, G. Li, J. Y. Liao, 
S. L. Xiong, C. Z. Liu, X. F. Li, Z. W. Li, Z. Chang, A. M. Zhang, 
Y. F. Zhang, X. F. Lu, C. L. Zou (IHEP), Y. J. Jin, 
Z. Zhang (THU), T. P. Li (IHEP/THU), F. J. Lu, L. M. Song, 
M. Wu, Y. P. Xu, S. N. Zhang (IHEP), 
report on behalf of the Insight-HXMT team: 

Insight-HXMT was taking data normally around the GW trigger time
(T0=2019-04-25 08:18:05.017 UTC). At T0, about 46% of the LIGO
localization region was covered by the Insight-HXMT without occultation
by the Earth.

Within T0 �� 100 s, no significant excess events (SNR > 3 sigma) are 
found in a search of the Insight-HXMT/HE raw light curves.

Assuming the GW counterpart GRB with three typical GRB Band spectral 
models, two typical duration timescales(1 s, 10 s) from the peak 
position of the LIGO-Virgo location probability map, the 5-sigma 
upper-limits fluence (0.2 - 5 MeV, incident energy) are reported below:

Band model 1 (alpha=-1.9, beta=-3.7, Ep=70 keV):
1s: 6.5e-08 erg cm^-2   
10s: 1.9e-07 erg cm^-2 

Band model 2 (alpha=-1.0, beta=-2.3, Ep=230 keV):
1s: 1.3e-07 erg cm^-2   
10s: 3.0e-07 erg cm^-2

Band model 3 (alpha=-0.0, beta=-1.5, Ep=1000 keV):
1s: 4.0e-07 erg cm^-2  
10s: 6.7e-07 erg cm^-2 

Further analysis will be reported in the following circulars.

All measurements above are made with the CsI detectors operating in the
regular mode with the energy range of about 80-800 keV (record energy).
Only gamma-rays with energy greater than about 200 keV can penetrate
the spacecraft and leave signals in the CsI detectors installed inside
of the telescope.

Insight-HXMT is the first Chinese space X-ray telescope, which was 
fundedjointly by the China National Space Administration (CNSA) and 
the Chinese Academy of Sciences (CAS). 
More information could be found at: http://www.hxmt.org.

C. D. Kilpatrick, D. A. Coulter, C. Rojas-Bravo, J. S. Brown, G. Dimitriadis,
R. J. Foley, T. Hung, D. O. Jones, M. R. Siebert, K. Siellez (UCSC),
A. L. Piro (Carnegie), A. Rest (STScI), M. Drout (University of Toronto)

report on behalf of the One Meter, Two Hemisphere (1M2H) collaboration:

Using the 1-m Swope telescope at Las Campanas Observatory, we obtained
images of ZTF19aarzaod and ZTF19aarykkb (Kasliwal et al., GCN 24191
Loading...
 
 ) in the
localization region of LIGO/Virgo S190425z (LIGO-Virgo Collaboration,
GCN 24168
Loading...
 
 ). We processed the data using photpipe (Rest et al., 2005)
calibrating to the Pan-STARRS system (Chambers et al., 2016).  We performed
PSF photometry on the images and did not perform any template subtraction.

Target       | UTC                 | Filter | Mag (Err)
ZTF19aarykkb | 2019-04-26 04:23:04 | r      | 18.4 (0.1)
ZTF19aarykkb | 2019-04-26 04:28:49 | i      | 18.2 (0.1)
ZTF19aarykkb | 2019-04-26 04:34:45 | g      | 19.2 (0.1)
ZTF19aarzaod | 2019-04-26 04:45:24 | r      | 20.1 (0.1)
ZTF19aarzaod | 2019-04-26 04:56:44 | i      | 19.5 (0.1)

Note: Given the level of background emission and lack of template subtractions,
we caution a systematic uncertainty of 0.1 mag.

We note that all fluxes are similar to previous reports (Hiramatsu et al.,
GCN 24194
Loading...
 
 ).  In particular, we note that ZTF19aarykkb has a similar r-band
magnitude at 2019-04-25 17:53:45 UT (Tan et al., GCN 24193
Loading...
 
 ) and g-band
magnitude at 2019-04-25 19:21:09 UT (Hiramatsu et al., GCN 24194
Loading...
 
 ).  We do not
see evidence for significant fading as reported by Bhalerao et al. (Bhalerao
et al., GCN 24201
Loading...
 
 ).

The reported photometry is consistent with SNe II at z ~ 0.025, as suggested
by their spectra (Pavana et al., GCN 24200
Loading...
 
 ; Perley et al., GCN 24204
Loading...
 
 ; Buckley
et al., GCN 24205
Loading...
 
 ; Izzo et al., GCN 24208
Loading...
 
 ; Wiersema et al., GCN 24209
Loading...
 
 ; Nicholl
et al., GCN 24211
Loading...
 
 ).

M. Nicholl, P. Short (Edinburgh), J. Anderson (ESO), T.-W. Chen (MPE), C. Inserra (Cardiff), O. Yaron (Weizmann), D. R. Young, S. J. Smartt (QUB), C. Angus, M. Pursiainen, P. Wiseman (Southampton), S. Taubenberger (MPA), M. Gromadzki (Warsaw) on behalf of the ePESSTO+ collaboration

We report observations of two possible counterparts to the LIGO/Virgo gravitational wave trigger S190425z (GCN 24168
Loading...
 
 ), under the the advanced Public ESO Spectroscopic Survey for Transient Objects (ePESSTO+; see Smartt et al. 2015, A&A, 579, 40 http://www.pessto.org). The observations were performed on the ESO New Technology Telescope at La Silla with the EFOSC2 instrument.

ZTF19aarzaod/AT2019dzw
Loading...
 
  was announced by Kasliwal et al. (GCN 24191
Loading...
 
 ) as a promising candidate from a ZTF search of the field. Follow-up spectroscopy by Buckley et al. (GCN 24205
Loading...
 
 ), Izzo et al. (GCN 24208
Loading...
 
 ) and Wiersema et al. (GCN 24209
Loading...
 
 ) indicated the transient is a young Type II supernova. Our NTT spectrum shows a broad feature consistent with H-alpha at the redshift of the host galaxy (z=0.028).

ATLAS19hwn/AT2019ebm
Loading...
 
  was announced by McBrien et al. (GCN 24197
Loading...
 
 ) as a marginal candidate identified during targeted imaging of the localisation region by ATLAS. Follow up observations by Perley et al. (GCN 24202
Loading...
 
 ) did not recover the reported source to a limit of r>22.0 mag. We obtained deep imaging to look for a rapidly fading transient. A 5x200s observation in r band shows no source at this position, with preliminary analysis indicating a limit of r>23 mag.

K. W. Smith, D. R. Young, O. McBrien, J. Gillanders. S. Srivastav,
S. J. Smartt, D. O'Neil, P. Clark, S. Sim (QUB), K. C. Chambers ,
M. Huber, E. Magnier, A. Schultz, (IfA, Univ. Hawaii), L. Denneau,
H. Flewelling, A. Heinze, J. Tonry, H. Weiland, A. Rest (STScI),
B. Stalder (LSST), C. Stubbs (Harvard)

We report observations of the BAYESTAR skymap of the BNS event S190425z
(The LIGO Scientific Collaboration and the Virgo Collaboration, GCN 24168
Loading...
 
 )
with the Pan-STARRS1 telescope (Chambers et al. 2016, arXiv:1612.05560
Loading...
 
 C).
Images were taken in the PS1 i-band (Tonry et al. 2012, ApJ 750, 99) and at
each pointing position a dithered sequence of 4 x 45 sec was taken. These
dithered sequences were repeated, with overlaps, to map 1258.10 square
degrees of the bayestar map 90% credible region and covered a sky region
totalling of 28.1% of the event's localisation likelihood. We began taking
data at 2019-04-25 09:39:48 (UTC).

The images were processed with the IPP (Magnier et al. 2016, arXiv:1612.05240
Loading...
 
 )
and difference images for the co-added stacks were produced using the
Pan-STARRS1 Science Consortium 3Pi data to detect transient objects. Standard
filtering procedures, combined with a machine learning algorithm (Wright et al.
2015, MNRAS, 449, 451) were applied and all candidates were spatially cross-
matched with known minor planets, and major star, galaxy, AGN and multi-
wavelength catalogues (as described in Smartt et al. 2016, MNRAS, 462 4094).

We report the following transients (bPC denotes the probability contour within
which the transient is found according to the bayestar.fits map).

Name      | PS Name | RA (J2000)  | Dec (J2000) |   z   | Disc Mag | bPC | Notes
AT2019ebu
Loading...
 
  | PS19pp  | 14 19 49.43 | +33 00 21.7 |       |  20.77 i | 30  |
AT2019ebw
Loading...
 
  | PS19pq  | 15 02 17.02 | +31 14 51.6 |       |  20.92 i | 10  |
AT2019ebv
Loading...
 
  | PS19pr  | 15 02 41.20 | +29 12 01.7 |       |  20.98 i | 70  |
AT2019eby
Loading...
 
  | PS19ps  | 15 10 15.68 | +33 04 17.6 |       |  20.22 i | 10  |
AT2019ebz
Loading...
 
  | PS19pv  | 15 25 41.74 | +32 19 42.9 |       |  20.01 i | 10  |
AT2019ecc
Loading...
 
  | PS19pw  | 15 26 29.53 | +31 39 47.5 |       |  20.10 i | 10  |
AT2019ecb
Loading...
 
  | PS19px  | 15 32 23.52 | +31 04 19.2 | 0.066 |  21.15 i | 10  | (1)
AT2019ece
Loading...
 
  | PS19py  | 15 32 54.55 | +33 29 00.8 | 0.083 |  20.33 i | 20  | (2)
AT2019ecg
Loading...
 
  | PS19qa  | 15 35 02.10 | +31 08 02.6 |       |  21.56 i | 10  |
AT2019ecf
Loading...
 
  | PS19qb  | 15 37 22.53 | +31 35 24.5 |       |  20.67 i | 10  |
AT2019ech
Loading...
 
  | PS19qd  | 15 41 53.81 | +26 59 12.9 |       |  20.67 i | 10  |
AT2019eck
Loading...
 
  | PS19qe  | 15 44 24.53 | +32 41 11.0 |       |  20.81 i | 20  |
AT2019ecj
Loading...
 
  | PS19qf  | 15 45 42.22 | +31 32 42.5 |       |  20.67 i | 20  |
AT2019ecl
Loading...
 
  | PS19qg  | 15 48 11.85 | +29 12 07.1 |       |  20.51 i | 10  |
AT2019ebr
Loading...
 
  | PS19qj  | 16 35 26.48 | +22 21 36.4 | 0.152 |  19.79 i | 20  | (3)
AT2019ebo
Loading...
 
  | PS19qn  | 16 54 54.71 | +04 51 31.5 |       |  20.02 i | 10  |
AT2019ebp
Loading...
 
  | PS19qo  | 16 59 57.74 | +12 06 18.3 | 0.045 |  20.29 i | 20  | (4)
AT2019ebq
Loading...
 
  | PS19qp  | 17 01 18.33 | -07 00 10.4 |       |  20.40 i | 10  |
AT2019ebs
Loading...
 
  | PS19qq  | 17 09 58.27 | +07 35 44.6 |       |  20.81 i | 20  |
AT2019ebt
Loading...
 
  | PS19qr  | 17 11 35.79 | +09 48 05.6 |       |  20.07 i | 40  |

NOTES

(1) Probable host is 2MASX J15322384+3104169 at 286 Mpc (NED)
(2) Probable host is 2MASS J15325460+3328553 at 365 Mpc (NED)
(3) Coincident with the core of 2MASX J16352643+2221368 at 700 Mpc (NED)
(4) Probable host is 16595787+1206238 at 199 Mpc (GLADE)

K. Wiersema (Warwick), A.J. Levan (Radboud), M. Fraser (UCD), D.T.H. Steeghs (Warwick), P. Jonker (Radboud/SRON), D.B. Malesani (DAWN/NBI and DARK/NBI) and N.R. Tanvir (Leicester) report for a larger collaboration: 

"We obtained optical spectroscopy of ZTF19aarzaod (Kasliwal et al. GCN 24191
Loading...
 
 ) with the William Herschel Telescope (WHT) + ACAM spectrograph. Observations began at 01:34 UT for a total of 1200s and cover the wavelength range 4000-9000A. 

The spectrum shows a broad H-alpha feature at z=0.028 as noted by Buckley et al. (GCN 24205
Loading...
 
 ) and Izzo et al. (GCN 24208
Loading...
 
 ) which classifies it as an SN II, and indicates it is unlikely to be associated with LIGO/VIRGO S190425z. We note that despite its apparent origin as a core collapse supernova our spectra do not reveal any nebular emission lines close to the transient position that may be expected from the star formation that created the SN progenitor. 

We thank the WHT staff, in particular Lillian Dominguez for assistance with these observations ."

L. Izzo (IAA/CSIC), R. Carini (INAF-OAR),  S. Benetti (INAF-OAPd), S. Piranomonte (INAF-OAR), P. D'Avanzo, A. Melandri  (INAF-OAB), M.T. Botticella (INAF-OAC), 
V. D'Elia (ASI-SSDC), V. Testa (INAF-OAR), G. Greco (Urbino Univ.), S. Yang (INAF-OAPd), E. Brocato (INAF-OAAb, INAF-OAR), A. Harutyunyan, C. Padilla Torres (INAF-TNG) 
on behalf of GRAWITA report:

 
We observed ZTF19aarzaod, one of the two most promising counterpart candidates reported by the Zwicky Transient Facility (Kasliwal et al., GCN 24191
Loading...
 
 ) for the GW event S190425z (GCN 24168
Loading...
 
 ),  
with the 3.6m Italian TNG telescope (Canary Islands, Spain), equipped with the DOLORES camera in spectroscopic mode starting on 2019-04-26 at 01:47:38 UT. An optical spectrum, lasting 2700 s, 
was obtained using the grism LR-B (wavelength range ~ 400-800 nm). 
The spectrum shows a red continuum with a broad emission consistent with being Halpha at the redshift of the host galaxy (z=0.028; Kasliwal et al., GCN 24191
Loading...
 
 ). Our results are consistent with the 
findings reported by Buckley et al. (GCN 24205
Loading...
 
 ) and suggest that ZTF19aarzaod is not related to the GW event S190425z. 


We thank the TNG visitor E. Knudstrup.

Daichi Hiramatsu (LCO/UCSB), Craig Pellegrino (LCO/UCSB), Jamison Burke
(LCO/UCSB), D. Andrew Howell (LCO/UCSB), Iair Arcavi (Tel Aviv University),
Curtis McCully (LCO) on behalf of the Las Cumbres GW Follow-up Collaboration


We report 300s gri-band images of the following galaxies in the LIGO/Virgo
S190425z localization region (GCN 24168
Loading...
 
 ) with the Las Cumbres Observatory
1m and 2m telescopes at Siding Spring, Australia. We find no obvious
candidates after performing image subtraction using SDSS images as
templates. Additional galaxies continue to be observed from our South
African and Chilean sites.

Name                   RA(J2000)  DEC(J200)  Time(UT)            Filter
Limmag
CSCG136-080            236.975159 +25.729359 2019-04-25 13:16:33 i      21.7
CSCG136-080            236.975159 +25.729359 2019-04-25 13:22:16 r      21.9
CSCG136-080            236.975159 +25.729359 2019-04-25 13:27:58 g      21.0
NGC6240                253.245255 +2.400985  2019-04-25 12:52:57 i      21.4
NGC6240                253.245255 +2.400985  2019-04-25 12:58:42 r      21.8
NGC6240                253.245255 +2.400985  2019-04-25 13:04:26 g      22.0
NGC6051                241.236267 +23.932871 2019-04-25 13:50:21 i      21.5
NGC6051                241.236267 +23.932871 2019-04-25 13:56:06 r      21.9
NGC6051                241.236267 +23.932871 2019-04-25 14:01:51 g      22.1
NGC6086                243.148087 +29.484850 2019-04-25 14:15:41 i      20.0
NGC6086                243.148087 +29.484850 2019-04-25 14:21:24 r      18.8
NGC6086                243.148087 +29.484850 2019-04-25 14:27:06 g      21.3
2MASXJ16542402-0953212 253.600113 -9.889244  2019-04-25 14:55:41 i      18.2
2MASXJ16542402-0953212 253.600113 -9.889244  2019-04-25 15:01:23 r      19.6
2MASXJ16542402-0953212 253.600113 -9.889244  2019-04-25 15:07:04 g      18.2
CGCG137-045            242.276917 +24.870296 2019-04-25 13:35:30 i      22.0
CGCG137-045            242.276917 +24.870296 2019-04-25 13:41:13 r      22.7
CGCG137-045            242.276917 +24.870296 2019-04-25 13:46:56 g      22.6
CGCG137-066            243.740997 +21.938314 2019-04-25 13:30:47 i      20.7
CGCG137-066            243.740997 +21.938314 2019-04-25 13:36:32 r      21.8
CGCG137-066            243.740997 +21.938314 2019-04-25 13:42:17 g      21.7

Jamison Burke (LCO/UCSB), Daichi Hiramatsu (LCO/UCSB), Iair Arcavi (Tel
Aviv University), D. Andrew Howell (LCO/UCSB), Curtis McCully (LCO), Craig
Pellegrino (LCO/UCSB) on behalf of the Las Cumbres GW Follow-up
Collaboration

Beginning 2019-04-25 21:34:17 we obtained 14 g-, r-, and i-band images of
the GW optical counterpart candidate ZTF19aarykkb (Kasliwal et al. 2019,
GCN 24191
Loading...
 
 ) with the Las Cumbres Observatory 1m telescope at the South
African Astronomical Observatory. We present the following PSF photometry
of the target:

Datetime (UT)         JD                Filter  Mag          Magerr
2019-04-25 21:34:17   2458599.3987	g	18.79        0.03
2019-04-25 21:38:04   2458599.4013	g	18.79        0.02
2019-04-25 21:42:05   2458599.4041	r	18.18        0.03
2019-04-25 21:44:31   2458599.4058	r	18.18        0.03
2019-04-25 21:47:12   2458599.4076	i	17.95        0.04
2019-04-25 21:49:39   2458599.4093	i	17.96        0.04
2019-04-25 22:15:11   2458599.4271	g	18.80        0.03
2019-04-25 22:20:38   2458599.4309	g	18.82        0.02
2019-04-25 22:26:19   2458599.4348	i	17.93        0.05
2019-04-25 22:31:46   2458599.4386	i	17.97        0.05
2019-04-25 23:25:31   2458599.4759	g	18.97        0.03
2019-04-25 23:29:18   2458599.4785	g	18.95        0.03
2019-04-25 23:33:18   2458599.4813	r	18.12        0.04
2019-04-25 23:35:45   2458599.4830	r	18.14        0.03

These values disagree with the photometry presented in Bhalerao et al. 2019
(GCN 24201
Loading...
 
 ) despite the observations being contemporaneous. The g- and
r-band photometry presented here is roughly 0.3 magnitudes fainter, and the
i-band photometry is almost a full magnitude fainter.

D.A.H. Buckley (SAAO), S. W. Jha (Rutgers), J. Cooke (Swinburne), and M.
Mogotsi (SALT/SAAO) report on behalf of the SALT GW collaboration:

We obtained an 1600-sec spectrum of ZTF19aarzaod (=AT 2019dzw
Loading...
 
 ; Kasliwal et al.
2019, GCN 24191
Loading...
 
 ) with SALT (+RSS) using the PG0300 line grating. The target is
well detected with a red continuum and a broad (~8000 km/s FWHM) H-alpha
emission feature at the redshift of the host galaxy, z=0.028. The data are
consistent with ZTF19aarzaod being a type II supernova, with the red color
likely a result of the heavy Milky Way extinction A_V = 2.2 (Schlafly &
Finkbeiner 2011, ApJ, 737, 103).

D. A. Perley, C. M. Copperwheat, and K. L. Taggart (LJMU) report on 
behalf of the GROWTH collaboration:

We obtained two 600-second exposures of ZTF19aarykkb (Kasliwal et al., 
GCN 24191
Loading...
 
 ) using the Spectrograph for the Rapid Acquisition of 
Transients (SPRAT) on the 2m Liverpool Telescope.

The reduced 1D spectrum shows a broad (full-width ~ 15000 km/s) emission 
line centered at 6700 Angstroms, which we associate with broad H-alpha 
from the transient.  Narrow H-alpha emission at z=0.025 (likely from the 
host galaxy) is also detected.  We cannot confirm the presence of He II 
(tentatively reported by Pavana et al., GCN 24200
Loading...
 
 ) or any other 
significant features at this time.  These observations suggest that this 
source is a young Type II supernova, and is unlikely to be associated 
with the BNS merger S190425z (GCN 24168
Loading...
 
 ).








DisclaimerNone

D. A. Perley and C. M. Copperwheat (LJMU) report:

We acquired a short sequence (40 seconds each in g/r/i filters) of 
imaging at the locations of all five of the marginal ATLAS transients 
reported by McBrien et al. (GCN 24197
Loading...
 
 ) using IO:O on the 2m Liverpool 
Telescope.   We do not detect a significant source at the location of 
any of these transients.  Approximate 3-sigma upper limits (AB, 
calculated relative to SDSS or PS1 secondary standards) are:

Name       JD               magnitude
AT2019eao
Loading...
 
   2458599.47986    g > 22.1
AT2019eao
Loading...
 
   2458599.48069    r > 22.1
AT2019eao
Loading...
 
   2458599.48150    i > 21.2
AT2019ebn
Loading...
 
   2458599.49142    g > 22.1
AT2019ebn
Loading...
 
   2458599.49225    r > 22.2
AT2019ebn
Loading...
 
   2458599.49306    i > 21.8
AT2019ebm
Loading...
 
   2458599.51188    g > 22.3
AT2019ebm
Loading...
 
   2458599.51272    r > 22.0
AT2019ebm
Loading...
 
   2458599.51353    i > 21.7
AT2019ebl
Loading...
 
   2458599.51785    g > 22.3
AT2019ebl
Loading...
 
   2458599.51869    r > 22.1
AT2019ebl
Loading...
 
   2458599.51950    i > 21.8
AT2019dzv
Loading...
 
   2458599.52163    g > 22.2
AT2019dzv
Loading...
 
   2458599.52246    r > 21.7
AT2019dzv
Loading...
 
   2458599.52328    i > 21.7






DisclaimerNone

V. Bhalerao, H. Kumar, V. Karambelkar, G. Waratkar, Y. Sharma (IITB), G. C. Anupama (IIA) report on behalf of the GROWTH collaboration:

We observed the two most promising candidates reported by the Zwicky Transient Facility (Kasliwal et al., GCN 24191
Loading...
 
 ) for the follow up the GW candidate S190425z (GCN 24168
Loading...
 
 ) with the GROWTH-India telescope. We obtained multiple images in g, r, and i bands, with exposures ranging from 300 sec - 600 sec. Source photometry for ZTF19aarykkb is given below.

Date-Time	MJD	exptime	Filter	Magnitude	Magerr
2019-04-25 18:25:39	2458599.268	600	r	17.78	0.06
2019-04-25 18:06:40	2458599.255	600	r	17.82	0.08
2019-04-25 21:54:37	2458599.413	300	g	18.49	0.05
2019-04-25 22:01:34	2458599.418	300	g	18.46	0.05
2019-04-25 22:08:50	2458599.423	300	r	17.48	0.05
2019-04-25 22:40:29	2458599.445	600	i	16.99	0.04
2019-04-25 22:54:42	2458599.455	600	g	18.62	0.04
2019-04-25 23:06:41	2458599.463	600	g	18.36	0.17

We also observed ZTF19aarzaod multiple times with 3 exposures in g band, 4 r and 2 i band exposures respectively, each with an exposure time of 600 seconds. We see a weak source in the r and i band images, further analysis is underway. The source appears to be fading rapidly in all bands.

The GROWTH India Telescope (GIT) is a 70-cm telescope with a 0.7 degree field of view, set up by the Indian Institute of Astrophysics and the Indian Institute of Technology Bombay with support from the Indo-US Science and Technology Forum (IUSSTF) and the Science and Engineering Research Board (SERB) of the Department of Science and Technology (DST), Government of India (https://sites.google.com/view/growthindia/). It is located at the Indian Astronomical Observatory (Hanle), operated by the Indian Institute of Astrophysics (IIA).

Pavana M., G. C. Anupama, B. S. Kiran (IIA) and V. Bhalerao (IITB) report on behalf of a larger collaboration:

We observed the potential counterpart ZTF19aarykkb (Kasliwal et al., GCN 24191
Loading...
 
 ) to the GW candidate S190525z (GCN 24168
Loading...
 
 ) with the HFOSC instrument on the 2m Himalayan Chandra Telescope. We obtained 2x30min exposures in the g7 grism and 1x30min exposure in the g8 grism. Spectra were reduced following standard techniques in IRAF.

The spectra show a broad, relatively featureless, continuum. We see emission features corresponding to H alpha and He II (4686) at the host redshift of 0.024. At this time, host contamination cannot be ruled out. The He II feature, if confirmed, indicates a very hot source. Further spectroscopic follow-up observations are encouraged.

C. D. Bochenek (Caltech), S. R. Kulkarni (Caltech), D. McKenna (Caltech), K. Belov (JPL), V. Ravi (Harvard, Caltech)

STARE2 is an all-sky instrument located at the Owens Valley Radio Observatory (OVRO) and the Goldstone Deep Space Communications Complex designed to search for fast radio transients. STARE2 is sensitive to millisecond duration bursts of radio emission above 157 kJy, for a burst at zenith. The beam pattern of the instrument is attached. STARE2 regularly sees type IIIdm bursts from the Sun.

No candidate events were found within 3 hours of the event.

Observing frequency: 1280-1530 MHz
Time resolution: 65.536 microseconds
Maximum timescale STARE2 is sensitive to: 34 ms
Frequency resolution: 122.07 kHz
Dispersion measure search range: 5 pc cm^-3 - 3000 pc cm^-3

If the event happened at the location of ZTF19aarykkb (GCN 24191
Loading...
 
 ) and a millisecond duration burst, we limit the flux to < 1.5 MJy.

The sky at OVRO at the time of the event contains 57% of the LIGO localization region (GCN 24196
Loading...
 
 ).

Authors: Tomas Ahumada (UMD), Michael W. Coughlin (Caltech), Kai Staats
(Embry-Riddle University),  Richard G. Dekany
<https://arxiv.org/search/astro-ph?searchtype=author&query=Dekany%2C+R+G>
(Caltech), Dmitry A. Duev
<https://arxiv.org/search/astro-ph?searchtype=author&query=Duev%2C+D+A>
(Caltech), Michael Feeney
<https://arxiv.org/search/astro-ph?searchtype=author&query=Feeney%2C+M>
(Caltech), S. R. Kulkarni
<https://arxiv.org/search/astro-ph?searchtype=author&query=Kulkarni%2C+S+R>
(Caltech), Reed Riddle
<https://arxiv.org/search/astro-ph?searchtype=author&query=Riddle%2C+R>
(Caltech) on behalf of the KPED team and the Global Relay of Observatories
Watching Transients Happen (GROWTH) collaboration.

We used the Kitt Peak EMCCD Demonstrator (KPED) on the Kitt Peak 84-inch
telescope (Coughlin et al 2019b) to obtain 300 s r-band images for 10
galaxies in the 90% localization region of the S190425z LIGO/Virgo
detection (GCN 24168
Loading...
 
 ). The observations started 10:12 UT on 2019 April 25
(about ~1.9 hours after the event) and the median 5 sigma upper limit for
an isolated point source in our images was r > 20.8. No transients were
detected in any of the galaxies listed below:

           Name             |         R.A. |       Dec.

------------------------------------------------------------------------


NGC6166                       | 16:28:38.23 | 39:33:04.4

NGC4889                       | 13:00:08.13 | 27:58:37.2

CB-11.4459                     15:18:32.09  |  31:09:40.82

1200-07486009              | 15:12:12.73 |  31:54:36.17

J15122693+3224040
<http://simbad.u-strasbg.fr/simbad/sim-id?Ident=%4012318336&Name=2MASX%20J15122693%2b3224040&submit=submit>
    | 15:12:26.92 |  32:24:03.84

J151717.32+304801.3   | 15:17:17.33 |  30:48:01.33

J151303.42+325505.8   | 15:13:03.43 |  32:55:05.81

J15120209+3254551
<http://simbad.u-strasbg.fr/simbad/sim-id?Ident=%402909607&Name=2MASX%20J15120209%2b3254551&submit=submit>
    | 15:12:02.07 | 32:54:55.29

J15113637+3142477
<http://simbad.u-strasbg.fr/simbad/sim-id?Ident=%4011050786&Name=2MASX%20J15113637%2b3142477&submit=submit>
    | 15:11:36.34  | 31:42:47.31

J151109.81+313833.2   | 15:11:09.82  | 31:38:33.2


The KPED team thanks the National Science Foundation, the National Optical
Astronomical Observatory and the Murty family for support in the building
and operation of KPED.

O. McBrien, S. Smartt, K. W. Smith, D. R. Young, (Queen's University
Belfast), L. Denneau, H. Flewelling, A. Heinze, J. Tonry, H. Weiland,
(IfA, Univ. of Hawaii), J. Gillanders, S. Srivastav, D. O'Neil, P.
Clark, S. Sim (QUB), A. Rest (STScI), B. Stalder (LSST), C. Stubbs
(Harvard), E. Magnier, A. Schultz, , M. Huber, K. C. Chambers (IfA)

We report observations of the BAYESTAR skymap of the BNS event
S190425z (The LIGO Scientific Collaboration and the Virgo
Collaboration, GCN 24168
Loading...
 
 ) with the ATLAS telescope system (Tonry et
al. 2018, PASP, 13, 164505). ATLAS is a twin 0.5m telescope system on
Haleakala and Mauna Loa employing two filters cyan and orange. While
carrying out the primary mission for Near Earth Objects, we can adjust
the schedule rapidly to point at LVC gravitational wave skymaps.

Sequences of 30 sec images were taken in the ATLAS o bands, and at
each pointing position a sequence of quads (4 x 30 sec) was taken. The
images were processed with the ATLAS pipeline and reference images
subtracted from each one. Transient candidates were run through our
standard filtering procedures, combined with machine learning
algorithms (e.g. Wright et al. 2015, MNRAS, 449, 451). Candidates were
spatially cross-matched with known minor planets, and star, galaxy,
AGN and multi-wavelength catalogues (as described in Smartt et al.
2016, MNRAS, 462 4094, Stalder et al. 2017, ApJ, 850, 149).

We began observing the northern part of the skymap within the first
hour of the preliminary notice. ATLAS covered 2652 squ. degrees of the
bayestar map 90% credible region and covered a sky region totalling of
37.2% of the event's localisation likelihood. A single image reaches 
approximately o = 19.5 (5 sigma), 

We flagged 25 transients but all were either known, or we detected
previous flux in our own forced photometry in images before the explosion. 
These new objects were registered on the TNS. Users are referred there as
a reference point. 

No further convincing counterpart candidates were found above o =
19.5, which were plausibly associated with a galaxy within 100-200 Mpc
(i.e. less than 50 kpc separation). Our area did not cover the sky position of the two
ZTF candidates (see Kasliwal et al. GCN 24191
Loading...
 
 ).

In addition we report 5 marginal candidates. These are all orphans (not
matched with any known source), but require independent confirmation.
They are within the skymap (at least 30% contour). 

Name              | IAU Name | RA (J2000)  | Dec (J2000) | Disc. MJD | Disc Mag 
ATLAS19hxm |  AT2019dzv
Loading...
 
  |14:01:45.02 | +46:12:56.1 | 58598.42  |  19.23 o 
ATLAS19hyx  |  AT2019ebl
Loading...
 
  |14:32:31.53 | +55:45:00.1 | 58598.44  |  19.28 o 
ATLAS19hyo  |  AT2019eao
Loading...
 
  |13:01:18.63 | +52:09:02.1 | 58542.59  |  19.36 o 
ATLAS19hwn |  AT2019ebm
Loading...
 
  |12:59:58.58 | +29:14:30.7 | 58598.40  |  19.42 o 
ATLAS19hwh |  AT2019ebn
Loading...
 
  |13:54:47.42 | +44:46:27.3 | 58318.29  |  19.07 o 


This work has made use of data from the Asteroid Terrestrial-impact 
Last Alert System (ATLAS) project. ATLAS is primarily funded to search 
for near earth asteroids through NASA grants NN12AR55G, 80NSSC18K0284, 
and 80NSSC18K1575; byproducts of the NEO search include images and 
catalogs from the survey area. The ATLAS science products have been 
made possible through the contributions of the University of Hawaii 
Institute for Astronomy, the Queen's University Belfast, and the 
Space Telescope Science Institute.

M. M. Anderson (Caltech), T. A. Callister (Caltech), G. Hallinan (Caltech) on behalf of the OVRO-LWA collaboration.

We report contemporaneous observations of the localization region of the BNS gravitational wave event S190425z (GCN 24168
Loading...
 
 ) with the OVRO-LWA. The observations span from -1 hour to +3 hour relative to the merger time (2019-04-25 08:18:05.17 UT), with continuous coverage of approximately 57% of the probability region. This includes the locations of the 2 candidates identified in ZTF (GCN 24191
Loading...
 
 ). The OVRO-LWA is a low-frequency radio telescope operating from 28 MHz to 86 MHz, with an approximately 20,000 sq. deg. instantaneous field-of-view.

Data reduction and analysis have commenced investigating the possible presence of a low frequency prompt counterpart to the event (see Anderson et al. 2018, Callister et al. 2019).

LIGO/Virgo S190425z: CLU/NED Galaxies in the Localization Volume

David O. Cook (Caltech/IPAC), Angela Van Sistine (UW Milwaukee), Leo Singer (NASA/GSFC), Igor Andreoni (Caltech), Michael Coughlin (Caltech), Bob Aloisi (UW Milwaukee), Patrick R. Brady (UW Milwaukee), Rick Ebert (Caltech/IPAC), George Helou (Caltech/IPAC), David Kaplan (UW Milwaukee), Mansi M. Kasliwal (Caltech), Joseph M. Mazzarella (Caltech/IPAC), and Marion Schmitz (Caltech/IPAC)

On behalf of the Global Relay of Observatories Watching Transients Happen (GROWTH) collaboration and the NASA/IPAC Extragalactic Database (NED) Team.

We spatially cross-matched the LIGO/Virgo S190425z trigger sky localization (90% containment volume) with the Census of the Local Universe (CLU; Cook et al. 2017; arxiv:1710.05016) galaxy catalog and found 69288 galaxies within the volume. The CLU catalog is a compilation of galaxies with existing redshifts from many sources (e.g., NED, SDSS, etc) and new galaxies from a 3PI steradian narrow-band survey to look for redshifted Halpha emission out to 200 Mpc with the Palomar Oschin 48-inch telescope (Cook et al. 2017; arxiv:1710.05016). We list here the top 20 CLU-matched galaxies sorted by stellar mass (Mstar) whose location on the sky and distance falls in the 90% volume reported by the BAYESTAR probability sky map (Singer et al. 2016). We also list the dust-corrected star formation rates (SFRs) for galaxies with GALEX FUV detections (a 'nan' for those with no detection).

For a more extended list of galaxies in the 90% volume go to the NED Gravitational Wave Followup service at https://ned.ipac.caltech.edu/uri/NED::GWF/. This service provides downloadable galaxy lists and visualizations for candidate host galaxies. For each GW alert, these products are automatically generated and made available within minutes to expedite efficient electromagnetic followup observations. The NED top 20 list is sorted by 2MASS absolute K-band magnitude, but users can sort the entire list on a variety of other criteria (probability density, UV magnitudes, etc) after download.


          name              ra      dec   distmpc logsfr_fuv logmstar  dP_dV
------------------------ -------- ------- ------- ---------- -------- --------
         HIZOA J1822-21 275.5775 -21.1603  105.49        nan    12.52 3.12e-07
 2MASXi J0215532-232855  33.9721 -23.4821  155.60        nan    12.15 1.12e-07
2MASX J06090714+2150343  92.2798  21.8428   92.75        nan    12.14 2.89e-07
2MASX J05210136-2521450  80.2558 -25.3626  177.23       2.36    12.03 5.47e-08
           FAIRALL 0009  20.9407 -58.8058  195.77       1.83    11.95 3.91e-08
        HIZOA J1749-32A 267.2717 -32.4039  117.43        nan    11.95 7.06e-08
              LDCE 1285 271.5879 -25.4325  104.81        nan    11.92 1.69e-07
       IRAS  05223+1908  81.3187  19.1794  123.16        nan    11.87 1.75e-07
         ESO 250-G  012  63.2014 -46.6193  136.77       0.72    11.85 9.70e-08
                ARK 120  79.0476  -0.1498  138.25        nan    11.83 1.26e-07
2MASX J04444356-4433487  71.1814 -44.5635  195.96        nan    11.80 3.74e-08
         HIZOA J1752-32 268.0325 -32.6194   82.71        nan    11.72 5.58e-08
2MASS J17421439-0843195 265.5582  -8.7228   95.94        nan    11.71 2.22e-07
       IRAS  05589+2828  90.5446  28.4728  137.41        nan    11.66 5.27e-08
               NGC 5995 237.1040 -13.7578  104.91       1.42    11.61 6.35e-08
                 3C 120  68.2962   5.3543  137.45        nan    11.56 6.87e-08
2MASS J04145265-0755396  63.7195  -7.9277  158.89       1.53    11.55 5.89e-08
               MRK 0618  69.0927 -10.3761  148.03       1.66    11.52 8.09e-08
           CGCG 049-037 227.9241   4.4919  155.60      -0.73    11.51 9.24e-08
        HIZOA J1749-32B 267.4346 -32.5875   80.95        nan    11.51 5.46e-08


Table: Top 20 galaxies in CLU that fall in the 90% probability volume for S190425z sorted by stellar mass. Column descriptions are as follows. name: galaxy name. ra: RA (J2000, decimal degrees). dec: Dec (J2000, decimal degrees). distmpc: galaxy distance (Mpc). logsfr_fuv: log10 of the star formation rate (SFR, Msun per year), derived from GALEX All Sky Kron FUV magnitudes via the prescription of Murphy et al. (2011), corrected for internal dust extinction using a combination of GALEX FUV and 22um ALLWISE fluxes (Hao et al. 2011). logmstar: log10 of the galaxy stellar mass (Msun), estimated from 3.4um ALLWISE fluxes and a mass-to-light ratio of 0.5 (McGaugh & Schombert et al. 2015).

Daichi Hiramatsu (LCO/UCSB), Iair Arcavi (Tel Aviv University), Jamison
Burke (LCO/UCSB), D. Andrew Howell (LCO/UCSB), Curtis McCully (LCO), Craig
Pellegrino (LCO/UCSB) on behalf of the Las Cumbres GW Follow-up
Collaboration

On 2019-04-25 19:21:09 UT we obtained two g-band images of the GW optical
counterpart candidate ZTF19aarzaod (Kasliwal et al. 2019, GCN 24191
Loading...
 
 ) with
the Las Cumbres Observatory 1m telescope at the Siding Spring Observatory
in Australia. We detect the candidate with a magnitude of g = 21.3��0.14
(using PSF fitting), consistent with the Tan et al. (2019, GCN 24193
Loading...
 
 )
measurement.

Han-Jie Tan (NCU), Po-Chieh Yu (NCU), Chow-Choong Ngeow (NCU), Wing-Huen Ip
(NCU)

On behalf of Global Relay of Observatories Watching Transients Happen
(GROWTH) collaborations

We report the photometric measurements of two promising candidates
ZTF19aarykkb and ZTF19aarzaod (GCN 24191
Loading...
 
 ) associated with the gravitational
wave trigger S190425z (GCN 24168
Loading...
 
 ) using Lulin One-meter Telescope(LOT) in
Taiwan. The observations were conducted using g, r, i filters at 2019-04-25
15:57:19 UT, ~7.65 hours after the trigger, and 2019-04-25 17:25:43, ~9.12
hours after the trigger, respectively. Preliminary photometry were obtained
by calibrating with Pan-STARRS catalog.

We would like to thank the staff in Lulin Observatory for helping the
observations.

Summary of ZTF19aarykkb:
         UT                        Filter          Exp(s)
Mag (AB)
2019-04-25 15:58:49           g           180                18.84+/-0.04
2019-04-25 16:02:11           r             180                18.23+/-0.02
2019-04-25 16:05:33           i             180                17.92+/-0.02

Summary of ZTF19aarzaod:
2019-04-25 17:48:24         g                300                21.45+/0.47
2019-04-25 17:53:45         r                 300
 20.26+/-0.25
2019-04-25 17:41:56         i                 300
 19.93+/-0.13

Also, we searched for optical counterpart in 90% localization area of
LIGO/Virgo S190425z (GCN 24168
Loading...
 
 ). The observation started at 2019-04-25
12:27:23 UT, 249 minutes after the trigger, and 27 galaxies were observed
in R-band with 180 second exposure time. No obvious transient can be
identified brighter than R~20 mag (AB). The galaxy coordinates are listed
below.

RA(deg)   DEC(deg)
194.9152    +53.341
212.0897    +55.302
212.6985    +35.913
213.2136    +35.711
213.6132    +36.404
216.0865    +36.461
217.9843    +33.643
218.3270    +34.735
219.1718    +34.973
232.4191    +30.486
235.3749    +27.986
236.0957    +25.327
236.3709    +26.603
236.9752    +25.729
239.0161    +24.448
239.2193    +24.662
239.2199    +25.569
239.6450    +27.618
239.7168    +26.136
239.9651    +25.941
241.1394    +23.838
241.2978    +24.960
242.2803    +21.868
242.7183    +22.626
242.8088    +26.923
242.8782    +23.812
243.0847    +23.002

Sasada, M., Akitaya, H., Nakaoka, T. (Hiroshima U.), Yoshida, M. (NAOJ/Subaru),
Tanaka, M. (Tohoku U.), Tominaga N., Ohgami, T., Kaneko A. (Konan U.),
Itoh, R. (Bisei Astronomical Observatory), Sekiguchi, Y. (Toho U.),
Utsumi, Y. (Stanford U./SLAC), Morokuma, T., Niino, Y., Ohsawa, R. (U.
of Tokyo),
Murata, K. L. (Tokyo Tech), on behalf of J-GEM collaboration


We report our optical imaging observations of galaxies in the
localization region of the BNS gravitational wave event S190425z (The
LIGO Scientific Collaboration and the Virgo Collaboration, 2019, GCN,
24168) using the Faint Object Camera and Spectrograph (FOCAS; 6 arcmin
field-of-view in diameter; Kashikawa et al. 2002, PASJ, 54, 819) on
the 8.2-m Subaru telescope. We started our observations at UT
2019-04-25 11:46, about 3.5 hours after the event.

We observed 154 galaxies in total. The target galaxies are selected
from the list of potential host galaxies for this event (Dalya et al.
2019, GCN, 24171) around the central coordinate of the localization of
the gamma-ray pulses detected with INTEGRAL/SPI-ACS (Minaev et al.
2019, GCN, 24170). The list of the galaxies we observed is shown in
the table below.

We took ten-second r-band images for each galaxy with typical 5-sigma
depths of 23-24 mag. The obtained images are compared with the
Pan-STARRS r-band images (Chambers et al., 2016, arXiv:1612.05560
Loading...
 
 )
with similar or slightly shallower depths compared to our FOCAS
images. In these galaxies, we find no apparent transient objects that
are not registered in the IAU Transient Name Server
(https://wis-tns.weizmann.ac.il).

Galaxy name               RA Dec
2MASS16522624+2319575     16:52:26.24 +23:19:57.5
NGC6051                   16:04:56.70 +23:55:58.3
NGC6062                   16:06:22.80 +19:46:40.6
60191                     17:23:26.11 +23:38:39.5
NGC6308                   17:11:59.72 +23:22:48.3
57296                     16:09:15.67 +25:42:45.0
56144                     15:49:57.32 +20:48:18.6
UGC10138                  16:01:40.23 +21:21:10.6
UGC10153                  16:03:19.52 +20:38:12.5
57607                     16:14:57.83 +21:56:17.9
58028                     16:24:15.15 +20:11:00.9
56443                     15:56:33.64 +20:03:08.2
56713                     16:01:28.67 +22:25:39.6
NGC6203                   16:40:27.38 +23:46:29.1
57072                     16:05:29.16 +19:56:31.7
2MASS16313806+2047366     16:31:38.06 +20:47:36.6
58396                     16:30:47.15 +20:21:19.3
NGC6233                   16:50:15.72 +23:34:47.4
1683153                   16:32:58.94 +23:11:51.0
1745822                   16:09:51.84 +25:41:11.6
59087                     16:50:14.26 +23:26:28.4
58322                     16:29:17.35 +20:21:53.3
58537                     16:34:53.70 +23:12:42.2
UGC10224                  16:08:50.23 +22:02:33.4
2MASS18405128+2334077     18:40:51.28 +23:34:07.7
58006                     16:23:40.08 +24:28:26.6
1695642                   16:22:57.30 +23:53:35.9
1631905                   16:16:11.90 +20:36:45.1
UGC10834                  17:24:32.84 +20:23:53.0
1612380                   16:00:30.52 +19:59:07.0
55776                     15:40:37.22 +20:33:44.7
56150                     15:49:59.28 +20:48:20.6
UGC10260                  16:11:57.87 +20:55:24.4
NGC6075                   16:11:22.56 +23:57:54.5
57272                     16:08:33.84 +21:04:52.3
1635109                   15:44:24.00 +20:45:09.5
214459                    16:06:00.72 +20:50:50.2
2MASS16060593+2047032     16:06:05.93 +20:47:03.2
2MASS16072060+2058306     16:07:20.60 +20:58:30.6
3089913                   16:06:16.28 +21:03:49.2
PGC1626696                12:03:48.25 +20:24:58.9
56856                     16:03:17.78 +21:35:30.5
56706                     16:01:25.27 +21:55:57.5
1661347                   16:04:50.77 +21:59:23.3
214390                    15:35:04.81 +23:28:45.7
56084                     15:48:33.88 +22:58:20.8
57085                     16:05:36.81 +22:11:10.8
56652                     16:00:38.21 +22:32:37.0
57526                     16:13:25.54 +21:54:33.8
SDSSJ153858.32+234650.8   15:38:58.33 +23:46:50.8
2MASS16073961+2220315     16:07:39.61 +22:20:31.5
1671243                   16:05:23.40 +22:30:27.6
IC4573                    15:42:12.27 +23:48:00.5
57116                     16:05:58.62 +22:37:55.9
57420                     16:11:20.97 +22:22:31.3
56853                     16:03:13.71 +23:00:29.5
UGC10236                  16:10:05.09 +22:39:01.1
56252                     15:52:02.13 +23:44:02.7
UGC10066                  15:51:36.87 +23:47:24.1
1688132                   16:03:44.45 +23:28:55.4
57542                     16:13:46.01 +22:55:07.9
57472                     16:12:20.33 +23:00:07.0
56175                     15:50:38.65 +20:22:54.7
1623900                   16:04:43.49 +20:19:25.3
56534                     15:58:33.94 +20:11:06.3
UGC10060                  15:51:06.90 +20:12:09.2
3089914                   16:18:24.75 +20:53:23.9
1686786                   15:10:28.49 +23:24:14.4
PGC1689724                15:11:16.57 +23:34:20.9
2MASS16182990+2209489     16:18:29.90 +22:09:48.9
1684230                   15:50:20.24 +23:15:32.7
1690340                   15:43:51.42 +23:36:26.5
1668320                   16:19:07.19 +22:21:07.7
55690                     15:38:59.04 +23:46:54.0
1672257                   16:17:11.69 +22:33:46.9
57493                     16:12:42.77 +22:59:02.7
2MASS16141210+2307136     16:14:12.10 +23:07:13.6
57263                     16:08:23.52 +23:28:24.7
57265                     16:08:22.57 +23:28:46.7
56963                     16:04:36.61 +23:39:47.3
1691288                   16:04:59.95 +23:39:30.4
57021                     16:05:02.50 +23:40:08.5
56958                     16:04:33.46 +23:50:16.3
57003                     16:04:50.57 +23:58:30.3
57014                     16:04:59.47 +23:58:12.3
56887                     16:03:41.89 +24:05:42.5
1692398                   16:12:07.70 +23:43:04.9
UGC10256                  16:11:30.77 +23:48:42.3
56991                     16:04:46.81 +24:16:43.2
1694999                   16:12:14.17 +23:51:28.9
57105                     16:05:49.61 +24:10:32.8
1705857                   16:03:14.25 +24:22:23.2
57406                     16:11:14.38 +24:13:29.5
1717114                   16:04:16.27 +24:48:44.4
UGC10160                  16:03:54.24 +25:00:38.0
57029                     16:05:11.46 +24:57:36.7
56949                     16:04:35.57 +25:11:23.3
57293                     16:09:06.46 +24:52:13.0
1686035                   16:36:40.62 +23:21:36.5
58712                     16:39:41.29 +23:30:53.4
58345                     16:29:44.04 +23:21:10.6
UGC10320                  16:18:07.32 +21:03:58.9
58744                     16:40:50.93 +23:39:34.0
58371                     16:30:13.32 +23:04:11.1
58050                     16:24:45.01 +23:57:54.3
58363                     16:30:02.71 +23:21:16.1
56249                     15:52:05.66 +20:08:42.7
58360                     16:29:53.36 +20:13:57.6
60508                     17:34:06.29 +23:31:09.2
1642211                   16:21:09.60 +21:04:30.3
56874                     16:03:28.01 +20:17:32.3
PGC058850                 16:43:36.19 +20:13:53.8
1621936                   16:47:43.70 +20:15:48.6
56961                     16:04:35.71 +25:43:14.3
57893                     16:21:04.24 +21:20:26.3
NGC6201                   16:40:14.41 +23:45:55.0
58042                     16:24:34.15 +21:11:41.3
2MASS15503893+2023227     15:50:38.93 +20:23:22.7
1736488                   16:10:48.42 +25:26:12.6
60430                     17:31:15.29 +23:35:01.8
1614726                   15:57:32.18 +20:03:12.8
57765                     16:18:05.32 +21:33:12.9
NGC6062B                  16:06:18.93 +19:45:47.2
58415                     16:31:06.58 +23:49:57.7
1673429                   16:20:44.20 +22:38:00.7
2MASS16345531+2034432     16:34:55.31 +20:34:43.2
2MASS16320391+2045519     16:32:03.91 +20:45:51.9
57752                     16:17:49.42 +20:41:28.9
1638586                   16:27:04.49 +20:54:35.2
1685163                   16:33:32.29 +23:18:43.4
57391                     16:10:52.39 +22:37:32.2
1603948                   16:13:55.38 +19:44:45.9
56282                     15:52:43.13 +20:13:59.8
1692904                   16:52:11.03 +23:44:39.6
UGC10525                  16:44:04.21 +23:23:52.1
60413                     17:30:34.99 +23:37:28.9
57290                     16:09:07.26 +21:52:03.7
59153                     16:52:17.31 +23:18:01.5
2MASS16302400+2026011     16:30:24.00 +20:26:01.1
1667049                   16:02:25.59 +22:17:02.5
59213                     16:53:53.83 +20:35:51.8
1628794                   16:25:52.24 +20:29:19.8
57283                     16:08:58.14 +19:49:25.5
1657664                   16:19:02.35 +21:48:22.7
1632425                   16:25:00.27 +20:38:04.5
1612760                   15:57:33.04 +19:59:43.8
1688390                   16:29:48.38 +23:29:45.6
1664646                   16:05:13.92 +22:09:32.6
1610658                   16:05:32.29 +19:56:04.8
1727092                   16:11:38.16 +25:09:11.6
1736885                   16:03:52.36 +25:26:48.6
2MASS16282647+2341107     16:28:26.47 +23:41:10.7
3089915                   16:20:34.24 +21:12:08.7
1699245                   16:11:35.70 +24:04:35.6

Mansi M. Kasliwal (Caltech), Michael W. Coughlin (Caltech),  Eric C. Bellm
(UW), Leo P. Singer (NASA GSFC), K. De (Caltech),  Igor Andreoni (Caltech),
Dmitry Duev (Caltech), Shreya Anand (Caltech), Tomas Ahumada (UMD), S.
Bradley Cenko (NASA GSFC), D. Goldstein (Caltech), A. Ho (Caltech), D. A.
Perley (LJMU), V. Bhalerao (IITB),  H. Kumar (IITB), Y. Sharma (IITB), C.
Copperwheat (LJMU), Virginia Cunningham (UMD), Shaon Ghosh (UWM), Ariel
Goobar (OKC), David Kaplan (UWM), Jesper Sollerman (OKC), Joshua S. Bloom
(UCB), M. Bulla (OKC), Nobuyuki Kawai (Tokyo Tech), Yoichi Yatsu (Tokyo
Tech), Katsuhiro Murata (Tokyo Tech), Hidekazu Hanayama (IAO), Takashi
Horiuchi (IAO), G. C. Anupama (IIA),  M. Rigault (CNRS/IN2P3), C.
Barbarino(OKC), R. Biswas (OKC), D. Cook (Caltech), G. Helou (IPAC)

On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of
Observatories Watching Transients Happen (GROWTH) collaborations

We observed the localization region of the gravitational wave trigger
S190425z (GCN 24168
Loading...
 
 ) with the Palomar 48-inch telescope equipped with the
47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019). We
were already observing the GW localization region as part of routine survey
operations. A new tiling was automatically optimally determined and
triggered using the GROWTH Target of Opportunity marshal (Coughlin et al.
2019a, Kasliwal et al. 2019b). We started obtaining target-of-opportunity
observations in the g-band and r-band filters beginning at UT 2019-04-25
09:19:07.161. A total of 4327 square degrees covering 41% of the enclosed
probability were observed before 12-deg twilight and analyzed in real-time.
Each exposure was 30s with a typical depth of 20.4 mag.

The images were processed through the ZTF reduction and image subtraction
pipelines at IPAC to search for potential counterparts (Masci et al. 2019).
After rejecting stellar sources (Tachibana and Miller 2018) and moving
objects and applying machine learning algorithms (Mahabal et al. 2019),
several high-significance transient candidates were identified by our
pipeline in the area observed.

Our most promising candidates thus far are:
------------------------------------------------------------------------
 ZTF Name     | RA (deg)    | DEC (deg)  | Filter | Mag   | Magerr
--------------+-------------+------------+--------+-------+-------------
 ZTF19aarykkb |  258.341454 | -9.964466  | r      | 18.63 |    0.10
 ZTF19aarzaod |  262.791487 | -8.450722  | r      | 20.11 |    0.18
--------------+-------------+------------+--------+-------+-------------
ZTF19aarykkb is near 2MASX J17132113-0957536 at z=0.024. ZTF19aarzaod is
near 2MASX J17311017-0827103 at z=0.028. Both have no ZTF detections prior
to the reported binary neutron star merger time (although our most recent
upper limits are only from 2019 April 19). Both host galaxies are in the
Census of the Local Universe (CLU) galaxy catalog (Cook et al. 2017). Thus,
with the data in-hand, the position, redshift of putative host galaxy ,
age, color and luminosity of both events are consistent with the GW
trigger. The positions are also consistent with being in the region that
Fermi-GBM could not constrain (GCN 24185
Loading...
 
 ). Both candidates have not yet
been reported to the Transient Name Server.  We caution that we cannot rule
out these are young supernovae and spectroscopic follow-up is urgently
needed. Additional analysis and follow-up is ongoing.

Also, just as a reference, we also provide a list of relatively young
candidates whose first ZTF detection was within the past three days below,
including a magnitude measurement from tonight. We emphasize that all the
events listed below have recent previous detections with ZTF prior to the
gravitational wave event trigger time and are unlikely to be related to
S190425z (e.g., background supernovae, active galactic nuclei, foreground
CV).

------------------------------------------------------------------------
 ZTF Name     | RA (deg)    | DEC (deg)  | Filter | Mag   | Magerr
--------------+-------------+------------+--------+-------+-------------
 ZTF19aarzfoz |  235.600249 | 19.5876421 | g      | 19.90 |    0.21
 ZTF19aarpptk | 254.2036677 |  9.6049366 | g      | 18.10 |    0.05
 ZTF19aarywve | 250.9039956 | 17.5801296 | r      | 20.45 |    0.19
 ZTF19aarpfjs | 252.0464742 |  1.0668639 | r      | 18.93 |    0.10
 ZTF19aarkmsl |  242.401716 | 25.7497917 | r      | 19.40 |    0.18
 ZTF19aarppnl | 258.9096792 | 15.7457655 | g      | 19.80 |    0.11
 ZTF19aarpplo | 262.9779752 | 18.7380718 | g      | 19.74 |    0.17
 ZTF19aarypbv | 248.5874816 | 30.5050049 | g      | 20.48 |    0.29
 ZTF19aartzok | 238.9634555 | 36.3591878 | g      | 20.27 |    0.20
 ZTF19aarxvub | 265.2782205 |   8.470448 | r      | 19.53 |    0.13
 ZTF19aaryvld |  250.075357 |  9.1071601 | r      | 20.01 |    0.18
 ZTF19aarpzuh | 252.1452493 | 15.7402238 | r      | 20.19 |    0.16
 ZTF19aarprog | 248.5427404 | 19.6347848 | r      | 19.00 |    0.11
 ZTF19aarycpi | 245.0910206 |  18.348845 | r      | 19.20 |    0.10
 ZTF19aailtzw | 256.934132  |   2.948056 | r      | 18.50 |    0.08
------------------------------------------------------------------------

ZTF and GROWTH are worldwide collaborations comprising Caltech, USA; IPAC,
USA, WIS, Israel; OKC, Sweden; JSI/UMd, USA; U Washington, USA; DESY,
Germany; MOST, Taiwan; UW Milwaukee, USA; LANL USA; Tokyo Tech, Japan;
IIT-B, India; IIA, India; LJMU, UK and USyd, Australia. ZTF acknowledges
the generous support of the NSF under AST MSIP Grant No 1440341. GROWTH
acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert
distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert
filtering and follow-up co-ordination is being undertaken by the GROWTH
marshal system (Kasliwal et al. 2019).

Dong Xu, Zi-Pei Zhu, Bang-Yao Yu, Tian-Meng Zhang, Xu Zhou, Xiao-Ming 
Teng, Peng-Fei Liu, Xiang-Nan Guan (NAOC), Sheng Yang (INAF-OAPd), 
Hai-Bin Zhao, Bin Li (PMO), Jin-Zhong Liu, Hu-Biao Niu, Jun-Hui Liu, 
Xuan Zhang (XAO), Ji-Rong Mao, Jin-Ming Bai (YNAO), Xing Gao (Urumqi 
No.1 Senior High School) report on behalf of the GWFUNC
collaboration:

We performed the search for the optical counterpart of LIGO/Virgo 
S190425z (GCN 24168
Loading...
 
 ) using the 0.9-m Schmidt telescope located at 
Xinglong, Hebei, China. Observations started at 12:40:09 UT on 
2019-04-25 and ended at 13:42:18 UT on 2019-04-25, and the 1.5 x 1.5 
deg^2 imager scanned high probability regions of the LVC localization 
that are accessible to the Xinglong/Schmidt telescope. The unfiltered 
images were taken with 60 sec exposure time and typical limiting depth 
is around 18 mag.

The searching was stopped by growing heavy clouds. Listed below are the 
field centers
observed.

RA(J2000)      DEC(J2000)
15:01:34.100 +29:55:26.00
15:01:29.990 +31:25:33.00
15:01:30.100 +32:55:36.00
15:08:22.990 +29:55:27.00
15:08:33.290 +31:25:29.00
15:08:37.090 +32:55:24.00
15:15:20.500 +29:55:46.00
15:15:34.890 +31:25:28.00
15:15:40.000 +32:54:55.00
14:43:21.790 +34:25:01.00
14:43:19.900 +35:54:50.00
14:43:19.590 +37:24:42.00
14:50:26.690 +34:25:58.00
14:50:44.790 +35:55:17.00
14:50:38.800 +37:24:51.00
14:57:44.190 +34:25:15.00
14:58:09.000 +35:55:29.00
14:58:07.900 +37:25:22.00
15:22:27.600 +29:55:45.00
15:22:37.500 +31:25:34.00
15:22:37.190 +32:55:04.00
15:29:39.890 +29:55:55.00
15:29:35.400 +31:26:06.00
15:29:39.600 +32:55:48.00
14:21:09.600 +34:24:48.00
14:21:03.590 +35:54:44.00
14:21:05.100 +37:24:14.00
14:28:32.890 +34:24:47.00
14:28:31.000 +35:54:32.00
14:28:30.400 +37:24:52.00
14:35:40.790 +34:24:50.00
14:35:55.700 +35:54:37.00
14:35:56.300 +37:23:56.00
15:06:26.900 +34:25:18.00
15:06:06.990 +35:55:32.00

Data analysis is ongoing. Optical transient(s) from the above fields, if 
interesting, will be
reported later.

Gregory S.H. Paek (SNU), Myungshin Im (SNU), Gu Lim (SNU), Insu Paek (SNU),
Suhyun Shin (SNU), Joonho Kim (SNU), Soojong Pak (KHU), Sungyong Hwang
(SNU), Bomi Park (SNU), Sophia Kim (SNU), Changsu Choi (SNU), Chung-Uk Lee
(KASI), Seung-Lee Kim (KASI), Hyung Mok Lee (KASI), on behalf of a larger
collaboration

We observed 13 host galaxy candidates with the 1.0-m telescope at the
Lemonsan Optical Astronomical Observatory(LOAO) in the 90% localization
area of S190425z, detected by LIGO/Virgo (GCN #24168
Loading...
 
 ).
The observation started at 2019-04-25 10:17:06 UT, and the images were
taken in R-band with 60 sec exposure time. No obvious transient has been
identified to a preliminary 3-sigma depth of R=19 AB mag. The list of the
inspected targets is given below.

NAME                    RA            DEC
IC4587                    239.965057    25.940653
2MASS+16582619-0319463    254.609146    -3.329548
PGC58097                246.408646    16.455
2MASS+17030866-0237020    255.786118    -2.617223
PGC55774                235.152664    28.512449
2MASS+16585063-1557280    254.710999    -15.957801
2MASS+17004803-0510264    255.200165    -5.17402
PGC55801                235.374939    27.986473
PGC1470081                247.533737    14.903552
NGC5567                    214.823303    35.138004
UGC10320                244.530502    21.066381
2MASS+16590728-0544311    254.780334    -5.741986
UGC10016                236.370865    26.603144

K. De (Caltech), S. M. Adams (Caltech), M. Coughlin (Caltech), M. M.
Kasliwal (Caltech), M. Hankins (Caltech), I. Andreoni (Caltech), S. Anand
(Caltech), L. Singer (NASA GSFC), , T. Ahumada (UMD),  A. Moore (ANU), J.
Soon (ANU), M. Ashley (UNSW), T. Travouillon (ANU)

report on behalf of the Palomar Gattini-IR team and the larger GROWTH
(Global Relay of Observatories Watching Transients Happen) collaboration

We report wide-field near-infrared follow-up observations of the
localization region of the BNS gravitational wave event S190425z (GCN
24168
Loading...
 
 ) by the Palomar Gattini-IR survey (Moore and Kasliwal 2019).
Gattini-IR is a newly commissioned near-IR camera with a field of view of
25 square degrees mounted on a robotic 30 cm telescope at Palomar
observatory.

Gattini-IR was already observing the GW localization region as part of
routine survey operations at the time of the trigger. We started customized
Target of Opportunity observations at UT 2019-04-25 09:12:09 (11 minutes
after initial notice time). The tiling was optimally determined and
triggered using the GROWTH Target of Opportunity marshal (Coughlin et al.
2019a, Kasliwal et al. 2019b). We imaged a total of 2401 square degrees,
covering 31% of the probability region of the event. Each field visit
consisted of a sequence of 8 dithers of 8 second exposures each on the
field, which were processed and stacked with the Palomar Gattini-IR data
reduction pipeline (De et al., in prep.). The typical limiting magnitude of
each stacked epoch (64 second exposure time) was between 15.5 - 16 AB mag
in J-band. Transient vetting is ongoing and any viable counterparts will be
announced.

G. Piano, C. Casentini (INAF/IAPS), F. Verrecchia (SSDC, and INAF/OAR), A.
Ursi, M.Cardillo (INAF/IAPS), M. Tavani (INAF/IAPS, and Univ. Roma Tor
Vergata), F. Lucarelli, C. Pittori (SSDC, and INAF/OAR), A. Bulgarelli, N.
Parmiggiani (INAF/OAS-Bologna), M. Pilia (INAF/OA-Cagliari), F. Longo
(Univ. Trieste, and INFN Trieste),

report on behalf of the AGILE Team:

In response to the LIGO-Virgo GW event S190425z at T0 = 2019-04-25 08:18:05
(UT), we performed a preliminary analysis of the AGILE Gamma-Ray Imaging
Detector (GRID). We divided the LIGO/Virgo localization region (LR) 90%
c.l. into two parts:
the first with R.A. in the approximate range between 1 - 8 hr, the second
with R.A. in the approximate range between 12 - 20 hr.

For the first part of the LR, we analyzed the first interval available with
a good coverage, between T0+100s and T0+200s. In this time interval, the
GRID exposure covered nearly 60% of the first part of the LR, observed at
off-axis angles between 25 deg and 70 deg. An analysis of the data in the
energy range 50 MeV - 10 GeV in this integration time was performed and
preliminary 3-sigma upper limits (ULs) values within the accessible
LIGO/Virgo LR are: from 4.1e-8 erg cm^-2 s^-1 to 4.5e-7 erg cm^-2 s^-1 for an
integration time of 100s.
In the time interval between T0-200 and T0+300, the GRID exposure covered
nearly 100% of the first part of the LR, observed at off-axis angles between
0 deg and 70 deg. An analysis of the data in the energy range 50 MeV - 10
GeV in this integration time was performed and preliminary 3-sigma ULs are:
from 1.4e-8 erg cm^-2 s^-1 to 3.2e-8 erg cm^-2 s^-1 for an integration time
of 500s.

Between T0+700s and T0+800s the GRID exposure covered nearly 15% of the
second part of the LR, observed at off-axis angles between 40 deg and 70
deg. An analysis of the data in the energy range 50 MeV - 10 GeV in this
integration time was performed and preliminary 3-sigma ULs are: from 4.2e-8
erg cm^-2 s^-1 to 2.3e-7 erg cm^-2 s^-1 for an integration time of 100s.
In the time interval between T0+700 and T0+2000, the GRID exposure covered
nearly 95% of the second part of the LR, observed at off-axis angles
between 40 deg and 70 deg. An analysis of the data in the energy range 50
MeV - 10 GeV in this integration time was performed and preliminary 3-sigma
ULs are: from 7.8e-9 erg cm^-2 s^-1 to 4.3e-8 erg cm^-2 s^-1 for an
integration time of 1300s.

These measurements were obtained with AGILE observing a large portion of
the sky in spinning mode.

C. Fletcher (USRA) reports on behalf of the Fermi-GBM Team and the
GBM-LIGO/Virgo group:

For S190425z and using the initial BAYESTAR skymap, Fermi-GBM was
observing 55.6% of the probability region at event time.

There was no Fermi-GBM onboard trigger around the event time of
the LIGO/Virgo detection of GW trigger S190425z (GCN 24168
Loading...
 
 ).
An automated, blind search for short gamma-ray bursts below the
onboard triggering threshold in Fermi-GBM also identified no
counterpart candidates. The GBM targeted search, the most
sensitive, coherent search for GRB-like signals, was run from
+/-30 s around merger time, and also identified no counterpart
candidates.

Assuming a detectable relativistic jet, it likely originated from the
44% of the LVC localization behind the Earth for Fermi, located at
RA=194.64, Dec=22.47 with a radius of 67.2 degrees. This region is
also consistent with the highest probability density region of the
BAYESTAR map. Otherwise, we set the following upper limits for the
remaining 90% localization region not blocked by the Earth. Using
the representative soft, normal, and hard GRB-like spectral templates
described in arXiv:1612.02395
Loading...
 
 , we set the following 3 sigma flux
upper limits over 10-1000 keV (in units of 10^-7 erg/s/cm^2):

Timescale  Soft     Normal   Hard
------------------------------------
0.1 s:     4.2-117  8.8-84.  27.-93.
1.0 s:     1.3-35.  2.7-25.  7.8-28.
10  s:     0.4-11.  0.9-7.7  2.4-8.7

Assuming the mean luminosity distance of ~155 Mpc from the GW
detection, we estimate intrinsic luminosity upper limits of
(0.03-5.1)E49 erg/s for the soft template, (0.04-3.4e)E49 erg/s
for the normal template, and (0.2-6.2)E49 erg/s for the hard template
over the 1 keV-10 MeV energy range.

T. Sakamoto (AGU), S. D. Barthelmy (NASA/GSFC),
A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL),
A. A. Breeveld (MSSL-UCL), A. P. Beardmore (U. Leicester),
D. N. Burrows (PSU), S. Campana (INAF-OAB), S. B. Cenko (NASA/GSFC),
G. Cusumano (INAF-IASF PA), A. D'Ai (INAF-IASFPA),
P. D'Avanzo (INAF-OAB), V. D'Elia(ASDC), S. Emery (UCL-MSSL),
P. A. Evans (U. Leicester), P. Giommi (ASI), C. Gronwall (PSU),
D. Hartmann (Clemson U.), J. A. Kennea (PSU), H. A. Krimm (NSF),
N. P. M. Kuin (UCL-MSSL), F. E. Marshall (NASA/GSFC),
A. Melandri (INAF-OAB), B. Mingo (U. Leicester), J. A. Nousek (PSU),
S. R. Oates (Uni. of Warwick), P. T. O'Brien (U. Leicester),
J. P. Osborne (U. Leicester), C. Pagani (U. Leicester),
K. L. Page (U.Leicester), M. Perri (ASDC),
J. L. Racusin (NASA/GSFC), B. Sbarufatti (INAF-OAB/PSU),
M. H. Siegel (PSU), G. Tagliaferri (INAF-OAB), A. Tohuvavohu (PSU),
E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift team:

We report the search results in the BAT data within T0 +/- 100 s of the
LVC event S190425z (LIGO/VIRGO Collaboration GCN Circ. 24168
Loading...
 
 ),
where T0 is the LVC trigger time (2019-04-25T08:18:05.000 UTC).

The center of the BAT FOV at T0 is
RA = 123.263 deg,
DEC = 22.657 deg,
ROLL = 279.608 deg.
The BAT Field of View (>10% partial coding) covers 7.26% of the integrated
LVC localization probability,  and 5.31% of the galaxy convolved
probability (Evans et al. 2016).

Within T0 +/- 100 s, no significant detections (signal-to-noise ratio
>~ 5 sigma) are found in the BAT raw light curves with time bins of 64 ms,
1 s, and 1.6 s. Assuming an on-axis (100% coded) short GRB with
a typical spectrum in the BAT energy range (i.e., a simple power-law model
with a power-law index of -1.32, Lien & Sakamoto et al. 2016), the 5-sigma
upper limit in the 1-s binned light curve corresponds to a flux upper limit
(15-350 keV) of ~ 8.01 x 10^-8 erg/s/cm^2.

No event data are available at this time.

BAT retains decreased, but significant, sensitivity to rate increases for
gamma-ray events outside of its FOV. About 45.73% of the integrated LVC
localization probability was outside of the BAT FOV but above the
Earth's limb from Swift's location, and the corresponding flux upper limits
for this region are within roughly an order of magnitude higher of those
within the FOV.

The results of the BAT analysis are available at
https://swift.gsfc.nasa.gov/results/BATbursts/team_web/S190425z/web/source_20190425.html

Myungshin Im (SNU), Gregory S. H. Paek (SNU),  Gu Lim (SNU), Insu Paek
(SNU), Suhyun Shin (SNU), Joonho Kim (SNU), Soojong Pak (KHU), Sungyong
Hwang (SNU), Bomi Park (SNU), Sophia Kim (SNU), Changsu Choi (SNU),
Chung-Uk Lee (KASI), Seung-Lee Kim (KASI), Hyung Mok Lee (KASI), on behalf
of a larger collaboration

We observed 30 host galaxy candidates in the 90% localization area of the
BNS merger candidate, S190425z, detected by LIGO/Virgo (GCN #24168
Loading...
 
 ) using
the SQUEAN instrument on the McDonald observatory's 2.1m telescope. The
observation started at 2019-4-25 09:38:57 UT, and the images were taken in
i-band with 120 sec exposure time. No obvious transient has been identified
to a preliminary 3-sigma depth of i=20.0 AB mag. The list of the inspected
targets is given below.

NAME       RA DEC
IC4587                      239.965057  25.940653
UGC10153                240.83136    20.636812
UGC10320                244.530502  21.066381
PGC58097                246.408646  16.455
2MASS+16590728-0544311  254.780334  -5.741986
UGC10016                236.370865  26.603144
PGC55801                235.374939  27.986473
PGC55774                235.152664  28.512449
2MASS+16585063-1557280  254.710999  -15.957801
2MASS+16582619-0319463  254.609146  -3.329548
2MASS+17004803-0510264  255.200165  -5.17402
2MASS+16572382-0147498  254.349258  -1.797175
2MASS+16574955-0156027  254.456467  -1.934085
2MASS+17030866-0237020  255.786118  -2.617223
2MASS+16550989+0551321  253.791245  5.858919
2MASS+16540875-0738073  253.536499  -7.635365
UGC10678                255.993729  24.177513
PGC58992                251.901932  8.752961
PGC1470081              247.533737  14.903552
PGC57472                243.084732  23.001947
PGC1688132              240.935242  23.482073
NGC6097                  243.608948  35.109116
NGC5567                  214.823303  35.138004
PGC51918                217.984253  33.642612
PGC1277972              252.051498  5.089275
PGC1112217              255.254517  -1.705736
IC1255                  260.77243    12.69542
6dFJ1654568-153135      253.736633  -15.526299
2MASS+16520774-1703135  253.032288  -17.053755
PGC59300                254.266769  5.372032

G. Hosseinzadeh, E. Berger, P. K. Blanchard, T. Eftekhari, J. Gill,
S. Gomez, L. Patton, V. A. Villar, P. K. G. Williams (Harvard U),
P. S. Cowperthwaite (Carnegie Obs), R. Chornock (Ohio U), W. Fong, 
R. Margutti (Northwestern U), and M. Nicholl (U Edinburgh) report:

We obtained 30 s g-band images of the following galaxies in the LIGO/Virgo
localization region of S190425z with the MMTCam instrument on the MMT 6.5-m
telescope:

Name              R.A.              Dec.        Date        UT
16545364-1657072  253.723525833333  -16.952021  2019-04-25  11:39:23.06
16571426-0613510  254.309417916667   -6.230837  2019-04-25  11:42:29.66
16520774-1703135  253.032287916667  -17.053755  2019-04-25  11:44:21.54
16590728-0544311  254.780334166667   -5.741986  2019-04-25  11:45:55.20
16580128-0149216  254.505370833333   -1.822693  2019-04-25  11:47:32.92
NGC6234           252.988937083333    4.383557  2019-04-25  11:49:28.05
59064             252.388167916667    6.016252  2019-04-25  11:51:21.12
59201             253.350372083333    4.23625   2019-04-25  11:52:39.44
16564688-0142052  254.195357916667   -1.701466  2019-04-25  11:54:11.67
UGC10426          247.709015         16.250687  2019-04-25  11:57:26.92
90265.0           254.36174         -10.191098  2019-04-25  11:59:13.75
NGC6225           252.08989           6.222765  2019-04-25  12:00:51.40
16462248+0902154  251.593704166667    9.037632  2019-04-25  12:02:05.10
16552449-0715255  253.852080833333   -7.25709   2019-04-25  12:04:56.52

Comparison of the images to the PS1 3pi survey (Chambers et al. 2016, 
arXiv:1612.05560
Loading...
 
 ) reveals no new sources brighter than ~21 mag.

We thank Mike Calkins and Ben Kunk at MMT for taking these observations.

I. Chelovekov, A. Pozanenko, P. Minaev, S. Grebenev on behalf of the IKI
GRB FuN collaboration report:

We used public data (observations of Inner Galaxy, proposal 1620021, PI 
A. Bodaghee) of IBIS-ISGRI/INTEGRAL to search for a possible 
EM-counterpart of the LIGO/Virgo S190425z event (LVC GCN #24168
Loading...
 
 ). We 
present our preliminary analysis of the prompt off-axis observation of 
the event with IBIS-ISGRI.

Around trigger time of S190425z (=G330561) the boresight angle was 30.8 
degrees. We found no significant emission above the background in the
time window -100 s + 100 s around the LIGO/Virgo S190425z trigger time.

In particular, we did not detect any positive signal near the time of a 
hard X-ray pulse detected by SPI-ACS/INTEGRAL(Martin-Carillo et al. GCN 
#24169
Loading...
 
 ; Minaev et al., GCN #24170
Loading...
 
 ; Savchenko et al., GCN #24178
Loading...
 
 ).

The upper limit of any possible emission with a duration of 1 s was (1.7 
+/- 0.8) x 10^{-6} erg / cm2 and (1.3 +/- 0.8) x 10^{-6} erg / cm2 in 
the energy ranges 30-100 and 100-500 keV, respectively. To estimate the 
flux we used our calibration based on several hundreds of GRBs 
synchronously detected by GBM/Fermi and on/off-axis by IBIS/ISGRI 
(Chelovekov et al, 2019, in press).

The light curves of IBIS/ISGRI and SPI-ACS can be found in

http://grb.rssi.ru/S190425z/S190425z_SPI-ACS.png
http://grb.rssi.ru/S190425z/S190425z_IBIS_1s.png

WeiKang Zheng, Keto Zhang, Sergiy Vasylyev and Alexei V. Filippenko
(UC Berkeley) report on behalf of the Lick/KAIT GW follow-up team:

The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at
Lick Observatory, observed the field of the gravitational-wave event
S190425z (GCN 24168
Loading...
 
 ) detected by LIGO/Virgo. More than one thousand
galaxies were selected from the Glade catalog (V1.0)
(http://aquarius.elte.hu/glade/)
according to their priority score. KAIT observed 101 of them based on
their priority scores and elevation visibility, with each clear-filter
exposure time being 60 s. The first image was taken at 09:06:22, Apr. 25 UT,
about 48 minutes after the trigger, and the last image at 12:43:52 UT.
Our typical limiting mag is 19.0. No viable counterparts were identified
and the analysis is ongoing. A full list of galaxies observed by KAIT is
given below.

GladeID  UT(Apr. 25)  RA (J2000)   Dec
-----------------------------------------------
G0613278 09:06:22     16:56:00.440 -16:58:54.80
G0628454 09:07:32     16:51:59.390 -15:02:08.50
G0609502 09:08:41     16:54:11.660 -16:19:16.90
G0748918 09:09:52     16:55:11.420 -07:39:56.40
G0667530 09:11:04     16:50:28.100 -17:40:35.60
G0757013 09:12:17     17:00:09.120 -05:46:12.50
G0559558 09:13:28     16:53:14.560 -17:05:05.10
G0585341 09:14:45     17:36:45.540 -07:42:16.50
G0726908 09:16:01     16:58:16.410 -06:15:33.60
G1850976 09:17:15     16:59:15.230 -21:18:09.90
G0590730 09:18:29     16:47:04.560 -23:29:07.70
G0276771 09:19:52     16:10:41.090 +22:33:54.90
G1851040 09:21:09     16:50:55.320 +09:24:14.30
G1478254 09:22:28     16:59:14.830 -21:18:11.30
G0586459 09:23:46     17:01:57.300 -01:52:22.00
G0507438 09:25:13     14:49:14.020 +34:55:06.60
G0566010 09:26:40     16:58:00.170 -18:42:57.40
G0683517 09:28:03     15:48:33.540 +28:35:01.90
G0004443 09:29:25     16:50:10.830 -17:40:41.70
G0731963 09:30:41     16:43:02.640 -30:04:59.50
G0662464 09:32:07     15:41:23.410 +28:17:59.00
G0708649 09:33:21     16:35:15.560 +21:30:07.00
G1851754 09:34:33     16:25:27.940 +19:27:48.90
G0741008 09:35:51     17:03:03.210 -02:52:38.50
G0584664 09:37:02     16:53:57.180 +02:22:12.10
G0650210 09:38:14     16:59:27.080 -03:21:27.30
G0758227 09:39:23     17:01:49.730 -05:12:04.00
G0558432 09:40:54     14:25:08.900 +36:22:28.00
G0663901 09:42:19     15:42:41.990 +28:04:24.00
G0670888 09:43:43     16:51:40.710 -14:50:18.20
G1335365 09:45:21     16:50:29.870 +05:59:02.60
G1487455 09:46:40     16:48:32.800 -20:10:29.00
G1851713 09:48:00     16:04:43.040 +24:57:33.60
G0611033 09:49:21     17:23:59.070 +12:40:43.10
G0711803 09:50:36     16:49:18.270 +06:11:23.10
G0012977 09:51:53     16:12:20.000 +23:45:45.90
G0663460 09:53:02     16:15:48.000 +21:53:28.30
G0737278 09:54:12     16:18:57.820 +21:01:13.10
G0557323 09:55:25     16:48:32.110 +08:43:10.00
G0824857 09:56:39     16:10:54.830 +22:36:02.70
G0739581 09:57:48     16:05:48.750 +23:55:08.10
G0660247 09:59:13     16:43:04.750 -24:58:53.80
G0618875 10:00:51     16:52:18.760 -14:55:05.10
G0663276 10:02:15     15:41:36.340 +28:13:53.10
G0751587 10:03:24     15:37:46.100 +29:44:45.80
G0618341 10:04:57     12:25:58.470 +28:27:06.00
G0601575 10:06:38     17:22:45.260 -00:48:48.20
G0623602 10:07:56     16:25:05.890 +20:08:24.10
G0814957 10:09:12     15:46:17.560 +26:32:37.80
G0618315 10:10:24     16:09:40.390 +21:59:33.80
G0558317 10:11:35     15:48:25.170 +26:00:17.50
G0663689 10:12:50     16:26:30.500 +16:24:44.50
G0681192 10:14:00     16:26:42.480 +16:31:59.50
G0752198 10:15:16     17:04:28.120 -04:18:28.40
G0455861 10:16:35     16:17:53.830 +18:47:47.50
G0692311 10:17:46     16:05:24.260 +25:08:18.40
G0158036 10:19:08     15:32:24.450 +40:48:01.00
G0784470 10:20:38     12:33:40.290 +29:36:21.10
G0771147 10:22:20     16:58:44.220 +27:49:33.00
G0758446 10:23:41     15:53:10.080 +24:34:12.00
G0734770 10:25:14     12:36:06.560 +29:38:15.70
G0019288 10:26:37     14:30:49.240 +36:16:33.90
G0605492 10:28:04     16:13:21.730 +29:26:10.60
G0700806 10:29:39     12:16:35.990 +23:52:25.60
G0124335 10:31:21     17:05:50.250 -06:16:50.10
G0610913 10:32:30     17:07:51.900 -05:26:15.00
G0698486 10:34:15     15:56:34.510 +24:26:18.30
G0642511 10:36:00     16:08:29.500 +22:17:30.30
G0494340 10:37:31     14:17:19.150 +39:30:01.20
G0617925 10:39:06     17:06:04.150 -04:37:17.10
G0947437 10:40:49     12:42:40.510 +34:57:25.50
G0622172 10:42:29     16:52:32.920 -03:07:40.10
G0810215 10:43:41     17:11:22.040 -03:15:10.80
G0475468 10:44:54     16:50:21.360 -16:54:39.60
G0013985 10:46:41     16:52:24.580 -02:28:56.20
G0789194 10:48:03     16:29:18.110 +39:30:37.80
G0730444 10:49:41     13:36:05.390 +34:34:43.60
G0822150 10:51:18     17:23:18.040 +02:00:02.30
G1053682 10:52:27     17:06:00.430 -01:34:00.00
G0586726 10:53:49     16:04:49.280 +25:54:12.80
G1308107 10:55:43     17:43:53.840 -09:43:55.50
G0396851 10:56:59     17:02:23.190 +06:53:58.30
G0598298 10:58:48     17:34:27.070 -03:22:44.20
G0395107 11:00:40     16:05:18.810 +17:41:54.30
G1851796 11:01:57     17:01:39.100 +10:14:58.80
G0728968 11:03:31     14:18:00.840 +35:19:13.50
G0157871 11:05:03     16:51:04.200 +23:32:51.40
G0597368 11:07:16     13:33:38.920 +41:46:22.30
G0650943 11:09:10     16:22:09.820 +36:19:53.40
G0796244 11:10:19     16:25:49.280 +40:50:57.70
G0603545 12:25:59     17:28:53.300 +03:13:43.30
G0799222 12:27:11     17:44:20.570 -01:41:28.50
G1487440 12:28:28     16:33:24.450 -28:07:56.80
G0717723 12:29:58     16:15:09.240 +35:03:43.30
G0819110 12:31:07     16:07:12.140 +36:37:51.40
G0719827 12:32:31     17:09:42.030 +03:52:13.80
G0566209 12:33:46     16:42:10.440 +13:21:19.70
G0726358 12:35:04     17:14:45.210 -06:05:54.90
G1172942 12:36:13     17:10:39.300 -06:52:45.30
G0624001 12:41:50     17:13:35.090 -05:36:45.60
G0584919 12:43:52     16:29:45.830 +17:50:59.10

V. Savchenko, C. Ferrigno (ISDC/UniGE, Switzerland)
A. Martin-Carillo (UCD, Dublin)
J. Rodi (IAPS-Roma, Italy)
A. Coleiro (APC, France)
S. Mereghetti (INAF IASF-Milano, Italy)

on behalf of the INTEGRAL multi-messenger collaboration:
https://www.astro.unige.ch/cdci/integral-multimessenger-collaboration

We detect only one possible low-S/N excess after correcting
for the local background variance at 2019-04-25T08:18:05
(T0)+6s, as reported in Martin-Carillo 2019 (GCN 24169
Loading...
 
 ).
Its fluence strongly depends on the true source location,
since large 90% localization region provided by LIGO/Virgo
includes sky directions in which INTEGRAL detectors able to
detect impulsive signal from all-sky (SPI-ACS and IBIS)
featured both low and high sensitivity.

For the excess at T0+6s, we estimate a possible 75-2000 keV
fluence range due to uncertainty of the location
from 2.0e-10 to 2e-9 erg/cm2 (in addition to systematic
uncertainty of response of 20% and statistical uncertainty of 30%),
assuming the duration of 1s and a characteristic short GRB spectrum
(an exponentially cut off power law with alpha=-0.5 and Ep=600 keV).

The sensitivity map is provided:

https://www.astro.unige.ch/cdci/content/int-combined-sensitivity-map-lvc-s190425z

We stress that the FAP of association of this excess to S190425z
is below 3 sigma. Further estimate of the FAP, taking into account detail
noise estimates during the days around the event, will be
provided in the future publications.

INTEGRAL is unable to provide an accurate localization of
the above mentioned low-S/N excess.
The best localization constraint we are currently able to
provide excludes the FoV of INTEGRAL/IBIS at the time of the event
(18:24:43.61, +29:45:25.9, 15 deg radius).
An event comparable to the excess at T0+6s occurring in the FoV
would have been detected by INTEGRAL/IBAS in realtime.
Furthermore, a location close to the FoV (within ~30 deg
from the center of the pointing) is discouraged by the lack
of INTEGRAL IBIS/PICsIT detection.

The south-west arc of the LIGO/Virgo localization of S190425z
is slightly unfavorable for the origin of the low-S/N excess,
if it is associated with the GW signal due to the absence
of any signal in IBIS/Veto shield.

Further analysis will be reported in the following circulars.

INTEGRAL has initiated a target of opportunity observation
of S190425z centered near peak of the LIGO/Virgo localization.
The results of these observations will be reported in
upcoming publications.

M. Sugizaki, N. Kawai (Tokyo Tech),  H. Negoro (Nihon U.),
M. Serino, S. Sugita (AGU),
M. Nakajima, W. Maruyama, M. Aoki, K. Kobayashi (Nihon U.),
S. Nakahira, T. Mihara, T. Tamagawa, M. Matsuoka (RIKEN),
T. Sakamoto, H. Nishida, A. Yoshida (AGU),
Y. Tsuboi, W. Iwakiri, R. Sasaki, H. Kawai, T. Sato (Chuo U.),
M. Shidatsu (Ehime U.), M. Oeda, K. Shiraishi (Tokyo Tech),
S. Ueno, H. Tomida, M. Ishikawa, Y. Sugawara, N. Isobe, R. Shimomukai,
M. Tominaga (JAXA),
Y. Ueda, A. Tanimoto, T. Morita, S. Yamada, S. Ogawa (Kyoto U.),
H. Tsunemi, T. Yoneyama, K. Asakura, S. Ide (Osaka U.),
M. Yamauchi, S. Iwahori, Y. Kurihara (Miyazaki U.),
T. Kawamuro (NAOJ), K. Yamaoka (Nagoya U.), Y. Kawakubo (LSU)
report on behalf of the MAXI team:

We examined the MAXI/GSC all-sky X-ray images (2-20 keV) obtained
in the orbit after the LVC trigger
S190425z at 2019-04-25 08:18:05.017 UTC (GCN 24168
Loading...
 
 ).

At the trigger time of S190425z, the high-voltage of MAXI/GSC was off,
and it was turned on at T0+1054 sec (=T0+17.5 min).
The one-orbit (92 min) scan of GSC covered > 90% of the 90% error region
of the bayestar skymap from 08:35:39 to 09:50:05 UTC (T0+1054 to T0+5520 sec).

No significant new source was found in the error region at the one-orbit scan.
The 1-sigma averaged upper limit obtained
from the scan was 20 mCrab at 4-10 keV.

If you require information of X-ray flux by MAXI/GSC at specific coordinates,
please contact the submitter of this circular by email.

M. J. B. Rosell, Matthew Shetrone, J. Craig Wheeler, Aaron Zimmerman, Chad Hanna, Lifan Wang, Greg Zeimann, and Richard Matzner on behalf of the LIGO Hobby-Eberly Telescope Response (LIGHETR) team report the spectroscopic observation of the field of S190425z (GCN #24168
Loading...
 
 ) with the VIRUS IFU array. We sampled a prioritized list of 5 galaxies from the GLADE catalog that overlapped with the LIGO probability map and the observable pupil of the HET. The resulting data cube covers the wavelength 350 to 550 nm with a resolving power of 750. The effective limiting magnitude in the B band was 22 magnitudes. Each field is 50x50 arc seconds. We observed, in order, galaxies:
254.780334-5.741986
254.505371-1.822693
253.245255+2.400985
241.236267+23.932871
247.400574+15.658440
Report of the results will be submitted later.


--
J. Craig Wheeler
Samuel T. and Fern Yanagisawa Regents Professor of Astronomy
University and University of Texas System Distinguished Teaching Professor
President, American Astronomical Society, 2006-2008
Department of Astronomy
2515 Speedway, Stop C1400
Austin, TX 78712-1205
512-471-6407
http://www.as.utexas.edu/~wheel

Supernova Explosions http://www.springer.com/us/book/9783662550526
Cosmic Catastrophes http://ebooks.cambridge.org/ebook.jsf?bid=CBO9780511536625
The Krone Experiment Krone Ascending http://www.amazon.com/Krone-Ascending-ebook/dp/B00926QEGW

The HAWC Collaboration (https://www.hawc-observatory.org) reports:

The HAWC Collaboration performed a follow-up of the gravitational wave
trigger S190425z (GCN #24168
Loading...
 
 ). At the time of the trigger the HAWC
local zenith was oriented towards (RA, Dec) = (240.1deg, 19.0deg).
48% of the GW candidate sky location probability fell within our
observable field of view (0-45 deg zenith angle).

We performed a search for a short timescale emission using 6 sliding
time windows (dt = 0.3s, 1s, 3s, 10s, 30s and  100s), shifted forward
in time by 20% of their width. We searched the 95% probability
containment area in a timescale-dependent time period, from t0-5dt to
t0+10dt, where t0 is the time of the GW trigger.

No significant gamma-ray detection above the background was observed.

The sensitivity of this analysis is greatly dependent on zenith angle,
ranging from 0deg to 45deg for the area searched in this
analysis. The 5sigma detection sensitivity to a 1s (100s) burst in the
80-800GeV energy range goes from 1.2e-6 erg/cm^2 to 1.1e-4 erg/cm^2
(6.4e-6 erg/cm^2 to 5.0e-4 erg/cm^2), depending on the zenith
angle.

HAWC is a TeV gamma ray water Cherenkov array located in the state of
Puebla, Mexico. It is sensitive to the energy range ~0.1-100TeV, and
monitors 2/3 of the sky every day with an instantaneous field-of-view
of ~2 sr.

On behalf of the HAWC collaboration.

Harm Schoorlemmer

Postdoctoral Researcher,
Max-Planck-Institut f��r Kernphysik,
Saupfercheckweg 1,
69117 Heidelberg,
Germany

phone +49 (0)6221 516 145

Michael J. Lundquist (UA), Kerry Paterson, Wen-fai Fong (Northwestern),
David J. Sand (UA), Stefano Valenti (UC Davis), Sheng Yang (INAF-OAPd, UC
Davis), Sam Wyatt (UA), Eric Christensen, Alex Gibbs, Frank Shelly
(UA/LPL), Jennifer Andrews (UA) report:

We initiated observations of 12 fields (each 2.26 x 2.26 deg^2) within the
LVC localization region for the GW trigger S190425z (LVC Circ 24168)
starting on 2019-04-25 9:01 UT. SAGUARO* uses the 1.5m Catalina Sky Survey
telescope on Mt. Lemmon, AZ and its 5 deg^2 imager to tile the highest
probability regions of the LVC localization that are accessible from
southern Arizona in order to search for electromagnetic counterparts to
gravitational wave events. The typical limiting magnitudes of single
pointings are G~21 mag (calibrated to Gaia DR2). Below are the field
centers observed. Any interesting transient candidates will be reported as
soon as possible.

RA DEC
244.2855 20.9792
245.7690 18.7708
247.2150 16.5625
242.7630 23.1875
240.4020 25.3958
237.9450 27.6042
235.4790 27.6042
237.9870 25.3958
240.3945 23.1875
247.9245 14.3541
249.3165 12.1458
235.3845 29.8125

*SAGUARO stands for Searches After Gravitational-waves Using ARizona's
Observatories. It is a partnership between the University of Arizona and
Northwestern University.

Gergely D��lya and Peter Raffai (Eotvos Univ.) reports on behalf of the
GLADE team:

We have found 45,033 galaxies in the GLADE catalog [1], within the 90% GW
localization area reported by the LVC in GCN 24168
Loading...
 
 , and within 155 +/- 45
Mpc
distance limits.

The galaxies found can be accessed on the GLADE website (12 MB txt file;
please note that the order of galaxies in the list only follow the ordering
as the appear in GLADE):
http://glade.elte.hu/O3/S190425z_GLADE_90_1sigma.txt

There are 13,330 galaxies within the 50% GW localization area and within
the same distance limits (3.6 MB txt file; please note that the order of
galaxies in the list only follow the ordering as the appear in GLADE):
http://glade.elte.hu/O3/S190425z_GLADE_50_1sigma.txt

[1] D��lya, G., Galg��czi G., Dobos, L. et al., 2018 MNRAS, 479, 2374

P. Minaev, A. Pozanenko, S. Grebenev, I. Chelovekov on behalf of IKI GRB FuN collaboration report:

We used public data of SPI-ACS to perform a search for possible EM-counterpart of LIGO/Virgo S190425z. Here we report preliminary analysis of SPI-ACS data available. After trigger time of S190425z (G330561) we found two pulses with time since trigger, duration, significance and fluence (in counts) above a background as following

+0.5 s, 0.4 s, 3.6 sigma, 900 +/- 250
+6 s, 1 s, 4 sigma, 1620 +/- 400

The significance of the second pulse is somewhat larger in comparison with reported early in GCN 24169
Loading...
 
  (Martin-Carillo et al.)
We estimated fluence of first and second pulses in the energy range  75 - 1000 keV as (9.0 +- 0.3) * 10^-8 erg/cm2 and (1.6 +- 0.4 ) * 10^-7
erg/cm2, respectively. It corresponds to E_iso (2.5 +/- 0.7) * 10^47 erg  and  (4.5 +/- 1.1) * 10^47 erg assuming distance 154.6 Mpc.

We do no found any extended emission up to T0+270 s after trigger.
The boresight of the center of the eror box localization (RA, Dec 16 10
18.75, 22 49 53.0609) is about 31 degrees.

A. Martin-Carillo (UCD, Dublin)
V. Savchenko, C. Ferrigno (ISDC/UniGE, Switzerland)
J. Rodi (IAPS-Roma, Italy)
A. Coleiro (APC, France)
S. Mereghetti (INAF IASF-Milano, Italy)

on behalf of the INTEGRAL multi-messenger collaboration:
https://www.astro.unige.ch/cdci/integral-multimessenger-collaboration

We investigated serendipitous INTEGRAL observations carried out at the
time of the LIGO/Virgo burst candidate S190425z.  The satellite was
covering the entire localization region of the LIGO-Virgo event with a sensitivity depending on the source position.
The best sensitivity depends on the source location.

We investigated the SPI-ACS and IBIS/PICsIT light curves between -30 and +30 s from
the trigger time (2019-04-25T08:18:05 UTC, T0) on temporal scales from
0.1 to 10s.

In the SPI-ACS or IBIS/PICsIT data, we do not detect a significant signal.
In SPI-ACS data, a marginally significant excess with S/N of 3.7 at is seen at T0+6s at the timescale of 1s.
Further analysis is ongoing, and will be reported in the coming circulars.

https://www.astro.unige.ch/cdci/integral/transients/lvc-s190425z

The LIGO Scientific Collaboration and the Virgo Collaboration report:

We identified the compact binary merger candidate S190425z during
real-time processing of data from LIGO Livingston Observatory (L1) and
Virgo Observatory (V1) at 2019-04-25 08:18:05.017 UTC (GPS time:
1240215503.017). The candidate was found by the GstLAL [1] and PyCBC
Live [2] analysis pipelines.

The signal-to-noise ratio (SNR) was below threshold in V1 so the
candidate was treated as a single-instrument event and no automated
preliminary notice was sent. Nonetheless, the V1 SNR is consistent
with the L1 data given the relative sensitivities of the detectors.
LIGO Hanford Observatory (H1) was offline at the time.

S190425z is an event of interest because its false alarm rate as
estimated by the online analysis is 4.5e-13 Hz, or about one in 7e4
years. The event's properties can be found at this URL:

https://gracedb.ligo.org/superevents/S190425z

The classification of the GW signal, in order of descending
probability, is BNS (>99%), Terrestrial (<1%), NSBH (<1%), BBH (<1%),
or MassGap (<1%).

Assuming the candidate is astrophysical in origin, there is strong
evidence for the lighter compact object having a mass < 3 solar masses
(HasNS: >99%). Using the masses and spins inferred from the signal,
there is strong evidence for matter outside the final compact object
(HasRemnant: >99%).

One skymap is available at this time and can be retrieved from the
GraceDB event page:
 * bayestar.fits.gz, an initial localization generated by BAYESTAR [3],
   distributed via GCN notice about 42 minutes after the candidate.

For the bayestar.fits.gz skymap, the 90% credible region is 10183
deg2. Marginalized over the whole sky, the a posteriori luminosity
distance estimate is 155 +/- 45 Mpc (a posteriori mean +/- standard
deviation). The skymap is coarser than usual due to the low
signal-to-noise ratio in V1; the localization is dominated by the L1
antenna pattern.

For further information about analysis methodology and the contents of
this alert, refer to the LIGO/Virgo Public Alerts User Guide
<https://emfollow.docs.ligo.org/userguide/>.

 [1] Messick et al. PRD 95, 042001 (2017)
 [2] Nitz et al. PRD 98, 024050 (2018)
 [3] Singer & Price PRD 93, 024013 (2016)

V. Lipunov, E. Gorbovskoy, V.Kornilov, D.Kuvshinov, N.Tyurina, P.Balanutsa,
A.Kuznetsov, V.V.Chazov, D. Vlasenko
Lomonosov Moscow State University,
Sternberg Astronomical Institute, Moscow State University

A. Tlatov, V.Senik, A.V. Parhomenko, D. Dormidontov
Kislovodsk Solar Station of the Pulkovo Observatory

K. Ivanov, O. Gres, N.M. Budnev, S. Yazev, O. Chuvalaev, V. Poleshchuk
Irkutsk State University

V. Yurkov, A. Gabovich, Yu. Sergienko
Blagoveschensk Educational State University, Blagoveschensk

R. Podesta, Carlos Lopez and F. Podesta
Observatorio Astronomico Felix Aguilar (OAFA)

Hugo Levato and Carlos Saffe
Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)

R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres
The Instituto de Astrofisica de Canarias

D. Buckley, S. Potter, A. Kniazev, M. Kotze
South African Astronomical Observatory



MASTER-OAFA robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Argentina (OAFA observatory of San Juan National University) started inspect of the LIGO/Virgo S190425z errorbox  3133 sec after trigger time at 2019-04-25 09:10:18 UT, with upper limit up to  17.9 mag. The observations began at zenit distance = 80 deg. The sun  altitude  is -24.3 deg. 

The galactic latitude b = -60 deg., longitude l = 98 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/ligo_1.php?id=10197

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

    3224 | 2019-04-25 09:10:18 |         MASTER-OAFA | ( 16h  8m 58.30s , +22d 53m 12.75s) |   C |   180 | 17.7 |        
    3482 | 2019-04-25 09:14:36 |         MASTER-OAFA | ( 16h  8m 58.90s , +22d 53m 17.07s) |   C |   180 | 17.9 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.