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LIGO/Virgo S190901ap

GCN Circular 25604

Subject
LIGO/Virgo S190901ap: Upper limits from IceCube neutrino searches
Date
2019-09-02T00:13:09Z (6 years ago)
From
Raamis Hussain at IceCube <raamis.hussain@icecube.wisc.edu>
IceCube Collaboration (http://icecube.wisc.edu/) reports:

Searches [1,2] for track-like muon neutrino events detected by IceCube
consistent with the sky localization of gravitational-wave candidate
S190901ap
 in a time range of 1000 seconds [3] centered on the alert event time
(2019-09-01 23:22:41.838 UTC to 2019-09-01 23:39:21.838 UTC) have been
performed.  During this time
period IceCube was collecting good quality data.  No significant track-like
events are found in spatial coincidence of S190901ap calculated from the map
circulated in the 1-Preliminary notice.

IceCube's sensitivity assuming an E^-2 spectrum (E^2 dN/dE) to neutrino
point sources within the locations spanned by the 90% spatial  containment
of S190901ap ranges from  0.029 to 1.150 GeV cm^-2 in a 1000 second
time window.

The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector
operating at the geographic South Pole, Antarctica. The IceCube realtime
alert point of contact can be reached at roc@icecube.wisc.edu


[1] Bartos et al. arXiv:1810.11467 (2018) and Countryman et
al.arXiv:1901.05486 (2019)
[2] Braun et al., Astroparticle Physics 29, 299 (2008)
[3] Baret et al., Astroparticle Physics 35, 1 (2011)

GCN Circular 25605

Subject
LIGO/Virgo S190901ap: No counterpart candidates in INTEGRAL SPI-ACS,prompt observation
Date
2019-09-02T00:18:14Z (6 years ago)
From
Enrico Bozzo at ISDC <Enrico.Bozzo@unige.ch>
E. Bozzo (ISDC/UniGE, Switzerland), S. Schanne (CEA, France)
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

Using INTEGRAL/SPI-ACS realtime data (following [1]) we have performed
a search for a prompt gamma-ray counterpart of S190901ap.

At the time of the event (2019-09-01 23:31:01 UTC, hereafter T0),
INTEGRAL was operating in nominal mode. The peak of the event
localization probability was at an angle of 61 deg with respect to the
spacecraft pointing axis. This orientation implies strongly suppressed
(21% of optimal) response of ISGRI, somewhat suppressed (46% of
optimal) response of IBIS/Veto, and near-optimal (87% of optimal)
response of SPI-ACS.

The background within +/-300 seconds around the event was rather
stable (excess variance 1.2).

We have performed a search for any impulsive events in INTEGRAL SPI-
ACS (as described in [2]) data.

We do not detect any significant counterparts and estimate a 3-sigma
upper limit on the 75-2000 keV fluence of 1.7e-07 erg/cm^2 (within the
50% probability containment region of the source localization) for a
burst lasting less than 1 s with a characteristic short GRB spectrum
(an exponentially cut off power law with alpha=-0.5 and Ep=600 keV)
occurring at any time in the interval within 300 s around T0. For a
typical long GRB spectrum (Band function with alpha=-1, beta=-2.5, and
Ep=300 keV), the derived peak flux upper limit is ~1.5e-07 (5.8e-08)
erg/cm^2/s at 1 s (8 s) time scale in 75-2000 keV energy range.

For the mean reported distance 242.0 Mpc this corresponds to the limit
on the total isotropic equivalent energy in 1 s of 1.2e+48 erg for
the short GRB spectrum and for a long GRB spectrum isotropic
equivalent luminosity in 1 s (8 s) of 1e+48 erg/s (4.1e+47 erg/s)

We report for completeness and in order of FAP, all excesses
identified in the search region. We find: 1 possibly associated
excess:

scale | T | S/N | luminosity ( x 1e+48 erg/s) | FAP
2.25 | 17.2 | 3.7 | 22.4 +/- 7.96 +/- 18.8 | 0.0343

4 likely background excesses:

scale | T | S/N | luminosity ( x 1e+48 erg/s) | FAP
0.1 | -6.37 | 3.5 | 9.72 +/- 3.82 +/- 8.16 | 0.469
0.55 | 171 | 4.8 | 5.74 +/- 1.62 +/- 4.82 | 0.544
0.1 | -23.9 | 4 | 11.1 +/- 3.83 +/- 9.29 | 0.808
0.1 | -28.8 | 4.1 | 11.4 +/- 3.84 +/- 9.58 | 0.831

Note that FAP estimates (especially at timescales above 2s) may be
possibly further affected by enhanced non-stationary local background
noise. This list excludes any excesses for which FAP is close to
unity.



All results quoted are preliminary.

This circular is an official product of the INTEGRAL Multi-Messenger
team.

[1] Savchenko et al. 2017, A&A 603, A46 [2] Savchenko et al. 2012, A&A
541A, 122S

GCN Circular 25606

Subject
LIGO/Virgo S190901ap: Identification of a GW compact binary merger candidate
Date
2019-09-02T00:18:29Z (6 years ago)
From
Shasvath J. Kapadia at U. of Wisconsin, Milwaukee <kapadia@uwm.edu>
The LIGO Scientific Collaboration and the Virgo Collaboration report:


We identified the compact binary merger candidate S190901ap during

real-time processing of data from LIGO Livingston Observatory (L1) and

Virgo Observatory (V1) at 2019-09-01 23:31:01.838 UTC (GPS time:

1251415879.838). The candidate was found by the GstLAL [1] analysis

pipeline.


S190901ap is an event of interest because its false alarm rate, as

estimated by the online analysis, is 7e-09 Hz, or about one in 4

years. The event's properties can be found at this URL:


https://gracedb.ligo.org/superevents/S190901ap


The classification of the GW signal, in order of descending

probability, is BNS (86%), Terrestrial (14%), BBH (<1%), MassGap

(<1%), or NSBH (<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 sky map is available at this time and can be retrieved from the

GraceDB event page:

 * bayestar.fits.gz, an updated localization generated by BAYESTAR

[2], distributed via GCN notice about 5 minutes after the candidate


For the bayestar.fits.gz sky map, the 90% credible region is 13613

deg2. Marginalized over the whole sky, the a posteriori luminosity

distance estimate is 242 +/- 81 Mpc (a posteriori mean +/- standard

deviation).


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] Singer & Price PRD 93, 024013 (2016)

GCN Circular 25607

Subject
LIGO/Virgo S190901ap: No counterpart candidates in HAWC observations
Date
2019-09-02T02:11:08Z (6 years ago)
From
Israel Martinez-Castellanos at UMD/HAWC <imc@umd.edu>
The HAWC Collaboration (https://www.hawc-observatory.org) reports:

The HAWC Collaboration performed a follow-up of the gravitational wave
trigger S190901ap (GCN #25606). At the time of the trigger the HAWC
local zenith was oriented towards (RA, Dec) = (236.1 deg, 19.1 deg).
31% 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 0 deg to 45 deg 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.

GCN Circular 25609

Subject
LIGO/Virgo S190901ap Global MASTER-Net observations report
Date
2019-09-02T03:58:08Z (6 years ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva, D.Kuvshinov 
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

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

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

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

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




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 S190901ap errorbox  7875 sec after trigger time at 2019-09-02 01:42:16 UT, with upper limit up to  19.2 mag. The observations began at zenit distance = 69 deg. The sun  altitude  is -43.8 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=10759

We obtain a following upper limits.  

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

    7966 | 2019-09-02 01:42:16 |         MASTER-OAFA | (01h 33m 01.151s , -36d 05m 50.60s) |   C |   180 | 17.5 |        
    8220 | 2019-09-02 01:46:30 |         MASTER-OAFA | (01h 30m 42.740s , -34d 05m 28.87s) |   C |   180 | 19.3 |        
    9275 | 2019-09-02 02:04:06 |         MASTER-OAFA | (01h 42m 53.530s , -36d 05m 18.14s) |   C |   180 | 16.4 |        
    9723 | 2019-09-02 02:11:33 |         MASTER-OAFA | (01h 40m 22.971s , -34d 05m 40.56s) |   C |   180 | 16.4 |        
   11293 | 2019-09-02 02:37:44 |         MASTER-OAFA | (02h 34m 46.030s , -32d 04m 54.73s) |   C |   180 | 18.4 |        
   11968 | 2019-09-02 02:48:58 |         MASTER-OAFA | (02h 53m 39.194s , -32d 04m 16.95s) |   C |   180 | 18.6 |        
   12192 | 2019-09-02 02:52:43 |         MASTER-OAFA | (02h 46m 42.695s , -28d 04m 41.93s) |   C |   180 | 18.5 |        
   12419 | 2019-09-02 02:56:29 |         MASTER-OAFA | (02h 55m 48.250s , -28d 04m 13.09s) |   C |   180 | 18.4 |        
   12644 | 2019-09-02 03:00:15 |         MASTER-OAFA | (02h 59m 15.321s , -30d 04m 29.16s) |   C |   180 | 18.4 |        
   12874 | 2019-09-02 03:04:05 |         MASTER-OAFA | (02h 52m 39.948s , -26d 04m 15.46s) |   C |   180 | 18.6 |        
   13324 | 2019-09-02 03:11:35 |         MASTER-OAFA | (03h 04m 50.900s , -28d 04m 21.90s) |   C |   180 | 18.5 |        
   13778 | 2019-09-02 03:19:09 |         MASTER-OAFA | (03h 08m 31.010s , -30d 03m 57.77s) |   C |   180 | 18.5 |        
   14227 | 2019-09-02 03:26:37 |         MASTER-OAFA | (03h 01m 32.460s , -26d 04m 24.25s) |   C |   180 | 18.9 |        
   15137 | 2019-09-02 03:41:48 |         MASTER-OAFA | (02h 40m 44.681s , -30d 04m 44.85s) |   C |   180 | 18.8 |        
Filter C is a clear (unfiltred) band. 


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

GCN Circular 25610

Subject
LIGO/Virgo S190901ap: Upper limits from Fermi-GBM Observations
Date
2019-09-02T05:11:21Z (6 years ago)
From
C. Michelle Hui at MSFC/Fermi-GBM <c.m.hui@nasa.gov>
C. M. Hui (NASA/MSFC) reports on behalf of the Fermi-GBM Team and the GBM-LIGO/Virgo group

For S190901ap and using the initial bayestar skymap, Fermi-GBM was observing 61% of the localization probability at event time.

There was no Fermi-GBM onboard trigger around the event time of the LIGO/Virgo detection of GW trigger S190901ap (GCN 25606). 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.

Part of the LVC localization region is behind the Earth for Fermi, located at RA=112.4, Dec=-9.7 with a radius of 67.2 degrees.  We therefore set upper limits on impulsive gamma-ray emission for the LVC localization region visible to Fermi at merger time. Using the representative soft, normal, and hard GRB-like templates described in arXiv:1612.02395, we set the following 3 sigma flux upper limits over 10-1000 keV, weighted by GW localization probability (in units of 10^-7 erg/s/cm^2):

Timescale  Soft     Normal   Hard
------------------------------------
0.128 s:     3.0     5.0     9.9
1.024 s:     0.9     1.5     3.5
8.192 s:     0.4     0.5     0.9

Assuming the median luminosity distance of 242 Mpc from the GW detection, we estimate the following intrinsic luminosity upper limits over the 1 keV-10 MeV energy range (in units of 10^48 erg/s):

Timescale  Soft     Normal   Hard
------------------------------------
0.128 s:     3.2          5.0        16.2
1.024 s:     1.0          1.5         5.7
8.192 s:     0.4          0.5         1.5

GCN Circular 25611

Subject
LIGO/Virgo S190901ap : no neutrino counterpart candidate in ANTARES search
Date
2019-09-02T06:46:23Z (6 years ago)
From
Thierry Pradier at ANTARES/IPHC/U of Strasbourg <tpradier@km3net.de>
M. Ageron (CPPM/CNRS), B. Baret (APC/CNRS), A. Coleiro (APC/Universite de Paris), M. Colomer (APC/Universite de Paris), D. Dornic (CPPM/CNRS), A. Kouchner (APC/Universite de Paris), T. Pradier (IPHC/Universite de Strasbourg) report on behalf of the ANTARES Collaboration:


Using on-line data from the ANTARES detector, we have performed a follow-up analysis of the
recently reported LIGO/Virgo S190901ap event using the 90% contour of the Initial bayestar probability
map provided by the GW interferometers (GCN#25606 <https://gcn.gsfc.nasa.gov/gcn3/25606.gcn3>). The ANTARES visibility at the time of the
alert, together with the 50% and 90% contours of the probability map are shown at http://antares.in2p3.fr/GW/S190901ap_Initial.png <http://antares.in2p3.fr/GW/S190901ap_Initial.png>.
Considering the location probability provided by the LIGO/Virgo collaborations, there is a
54.1% chance that the GW emitter was in the ANTARES **upgoing** field of view at the time of
the alert.

No up-going muon neutrino candidate events were recorded in the ANTARES sky during a
+/-500s time-window centered on the time 2019-09-01 23:31:01 and in the 90% contour of the S190901ap
event. The expected number of atmospheric background events in the region visible by ANTARES is
4.34e-03 in the +/- 500s time window. An extended search during +/- 1 hour gives no
up-going muon neutrino coincidence. The expected number of atmospheric background events in the
region visible by ANTARES is 3.12e-02 in this larger time window.

ANTARES is the largest undersea neutrino detector, installed in the Mediterranean Sea, and it is
primarily sensitive to neutrinos in the TeV-PeV  energy range. At 10 TeV, the median angular
resolution for muon neutrinos is about 0.5 degrees. In the range 1-100 TeV ANTARES has a
competitive sensitivity to this position in the sky.

GCN Circular 25612

Subject
LIGO/Virgo S190901ap: Coverage and upper limits from MAXI/GSC observations
Date
2019-09-02T07:32:02Z (6 years ago)
From
Motoko Serino at RIKEN/MAXI <motoko@crab.riken.jp>
M. Serino, S. Sugita (AGU), H. Negoro (Nihon U.), 
N. Kawai, M. Sugizaki (Tokyo Tech),
M. Nakajima, W. Maruyama, M. Aoki, K. Kobayashi (Nihon U.),
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. Nakahira, Y. Sugawara, S. Ueno, H. Tomida, M. Ishikawa, N. Isobe, R. Shimomukai, M. Tominaga (JAXA),
Y. Ueda, A. Tanimoto, S. Yamada, S. Ogawa, K. Setoguchi, T. Yoshitake (Kyoto U.),
H. Tsunemi, T. Yoneyama, K. Asakura, S. Ide (Osaka U.),
M. Yamauchi, S. Iwahori, Y. Kurihara, K. Kurogi, K. Miike (Miyazaki U.),
T. Kawamuro (NAOJ), K. Yamaoka (Nagoya U.), Y. Kawakubo (LSU) 
report on behalf of the MAXI team:

We examined MAXI/GSC all-sky X-ray images (2-20 keV) 
after the LVC trigger S190901ap at 2019-09-01 23:31:01.837 UTC (GCN #25606).

At the trigger time of S190901ap, the high-voltage of MAXI/GSC was on.
The instantaneous field of view of GSC at the GW trigger time covered 1% of the 90% credible region 
of the bayestar sky map, in which we found no significant new X-ray source.
The 4-orbit (360 min) observation with GSC after the event covered 72% 
of the 90% credible region of the bayestar skymap from 23:31:01 to 05:30:56 UTC (T0+0 to T0+21595 sec).

No significant new source was found in the region in the observation.
A typical 1-sigma averaged upper limit obtained in one scan observation
is 20 mCrab at 2-20 keV.

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

GCN Circular 25613

Subject
LIGO/Virgo S190901ap: No counterpart candidates in AGILE-MCAL observations
Date
2019-09-02T08:16:12Z (6 years ago)
From
Martina Cardillo at INAF-IAPS <martina.cardillo@inaf.it>
M. Cardillo (INAF/IAPS), F. Verrecchia (SSDC,and INAF/OAR), F. Longo (Univ. Trieste, and INFN Trieste), C. Pittori, F. Lucarelli (SSDC, and INAF/OAR), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), C. Casentini, G. Piano, A. Ursi (INAF/IAPS), A. Bulgarelli, V. Fioretti, N. Parmiggiani (INAF/OAS-Bologna), M. Pilia (INAF/OA-Cagliari), report on behalf of the AGILE Team:

In response to the LIGO/Virgo GW event S190901ap at T0 = 2019-09-01 23:31:01 (UT), a preliminary analysis of the AGILE minicalorimeter (MCAL) triggered data found no event  candidates within a time interval covering -/+ 15 sec from the LIGO/Virgo T0.

At the T0, about 60% of the S190901ap 90% c.l. localization region was accessible to the AGILE MCAL.Three-sigma upper limits (ULs) are obtained for a 1 s integration time at different celestial positions within the accessible S190901ap localization region, from a minimum of 1.31E-06 erg cm^-2 to a maximum of 7.28E-06 erg cm^-2 (assuming as spectral model a single power law with  photon index 1.5).

The AGILE-MCAL detector is a CsI detector with a 4 pi FoV, sensitive in the energy range 0.4-100 MeV. Additional analysis of AGILE data is in progress.

GCN Circular 25614

Subject
LIGO/Virgo S190901ap: Updated Sky Localization
Date
2019-09-02T12:05:35Z (6 years ago)
From
Peter Shawhan at U of Maryland/LSC <pshawhan@umd.edu>
The LIGO Scientific Collaboration and the Virgo Collaboration report:

We have conducted further analysis of the LIGO Livingston Observatory
(L1) and Virgo Observatory (V1) data around the time of the compact
binary merger (CBC) candidate S190901ap (GCN Circular
25606). Parameter estimation has been performed using LALInference [1]
and a new sky map, LALInference.v2.fits.gz, distributed via GCN
Notice, is available for retrieval from the GraceDB event page:

https://gracedb.ligo.org/superevents/S190901ap/

The preferred sky map at this time is LALInference.v2.fits.gz. For the
LALInference.v2.fits.gz sky map, the 90% credible region is 14753
deg2. Marginalized over the whole sky, the a posteriori luminosity
distance estimate is 241 +/- 79 Mpc (a posteriori mean +/- standard
deviation).

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)

GCN Circular 25616

Subject
LIGO/Virgo S190901ap: Candidates from the Zwicky Transient Facility
Date
2019-09-02T14:32:28Z (6 years ago)
From
Mansi M. Kasliwal at Caltech/Carnegie <mansikasliwal@gmail.com>
Erik Kool (OKC), Robert Stein (DESY), Yashvi Sharma (Caltech), Viraj
Karambelkar (Caltech), Mansi Kasliwal (Caltech), Daniel Perley (LJMU),
 Valery Brinnel (HU Berlin), Jakob Nordin (HU Berlin), Shreya Anand
(Caltech), Michael Coughlin (Caltech), Leo P. Singer (NASA GSFC), Igor
Andreoni (Caltech), Gaurav Waratkar (IITB), Harsh Kumar (IITB), Maitreya
Khandagale (IITB), Kunal Deshmukh (IITB), Varun Bhalerao (IITB), G. C.
Anupama (IIA), Dougal Dobie (USyd/CSIRO), Brad Cenko (NASA GSFC), Tomas
Ahmuda (UMD), Eric Bellm (UW), Albert Kong (NTHU), Anna Franckowiak (DESY),
Pradip Gatkine (UMD)

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
S190901ap (LVC et al. GCN 25606, GCN 25614) with the Palomar 48-inch
telescope equipped with the 47 square degree ZTF camera (Bellm et al. 2019,
Graham et al. 2019). The tiling was 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 beginning at UT 2019-09-02 03:08 UT.
We covered 44% of the enclosed probability based on the new lalinference
map (38% of the enclosed probability based on the initial bayestar map) in
6500 sq deg mapped before we had to close due to clouds. Each exposure was
30s with a typical depth of 20.7 mag.

The images were processed in real-time through the ZTF reduction and image
subtraction pipelines at IPAC to search for potential counterparts (Masci
et al. 2019). AMPEL (Nordin et al. 2019) was used to search the alerts
database for candidates. After rejecting stellar sources (Tachibana and
Miller 2018) and moving objects and applying machine learning algorithms
(Mahabal et al. 2019), and after removing candidates with history of
variability prior to the merger time, the following high-significance
transient candidates were identified by our pipeline in the 95%
localization of the new lalinference map (LVC et al. GCN 25614).

------------------------------------------------------------------------
 ZTF Name     | RA (deg)   | DEC (deg)  | Filter | Mag   | Magerr
------------------------------------------------------------------------
 ZTF19abvizsw | 279.472820 | +61.497984 | r      | 19.45 | 0.11
 ZTF19abvixoy | 279.552972 | +27.420935 | r      | 19.22 | 0.10
 ZTF19abvjnsm | 267.202697 | +44.693203 | r      | 20.23 | 0.20
 ZTF19abvionh | 253.750924 | +14.051330 | g      | 20.73 | 0.31
------------------------------------------------------------------------

ZTF19abvizsw has a red color (g-r ~ 0.5 mag), no underlying host in the
reference image and is on the outer periphery of the new LVC sky
localization. ZTF has observed this field every night for the past month as
part of routine survey operations and the first detections of this
transient are only after the binary neutron star merger time. ZTF19abvixoy
has an upper limit from Aug 30 UT and possibly a faint counterpart in PS1.
ZTF19abvjnsm has an upper limit from Sep 1 UT but its host galaxy has too
high a phot-z estimate from SDSS of 0.51 +/- 0.11. The host galaxy of
ZTF19abvionh has a consistent SDSS phot-z (0.064 +/- 0.016) but the two
detections last night are separated by only a short baseline of 7 minutes
(a moving object in our solar system cannot be ruled out for this
candidate). We encourage spectroscopic and photometric follow-up to discern
the nature of these transients.

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; SDSU, 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 database searches are done by AMPEL (Nordin
et al. 2019). Alert filtering and follow-up co-ordination is being
undertaken by the GROWTH marshal system (Kasliwal et al. 2019).

GCN Circular 25617

Subject
LIGO/Virgo S190901ap: no counterpart candidates in the Swift/BAT Observations
Date
2019-09-02T16:06:35Z (6 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
D. M. Palmer (LANL), S. D. Barthelmy (NASA/GSFC),
A. Y. Lien (GSFC/UMBC), T. Sakamoto (AGU),
A. P. Beardmore (U. Leicester), M. G. Bernardini (INAF-OAB),
A. A. Breeveld (MSSL-UCL), 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 (ASI-SSDC), 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), 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. J. Page (UCL-MSSL), M. Perri (ASDC),
J. L. Racusin (NASA/GSFC), B. Sbarufatti (INAF-OAB/PSU),
M. H. Siegel (PSU), G. Tagliaferri (INAF-OAB), A. Tohuvavohu (Toronto),
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 S190901ap (LIGO/VIRGO Collaboration GCN Circ. 25606),
where T0 is the LVC trigger time (2019-09-01T23:31:01.837 UTC).

The center of the BAT field of view (FOV) at T0 is
RA = 154.887 deg,
DEC = -39.451 deg,
and the roll angle is 7.936 deg.
The BAT FOV (>10% partial coding) covers 2.70% of the integrated
LVC localization probability, and 2.64% of the galaxy convolved
probability (Evans et al. 2016). Note that the sensitivity in the BAT FOV
changes with the partial coding fraction. Please see the BAT FOV figure
in the summary page (link below) for the specific location of the LVC
region relative to the BAT FOV.

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 ~ 1.39 x 10^-7 erg/s/cm^2.
Assuming a luminosity of ~ 2 x 10^47 erg/s (similar to GW170817)
and an average Epeak of ~ 400 keV for short GRBs (Bhat et al. 2016),
this flux upper limit corresponds to a distance of ~ 60.86 Mpc.

Event data is available from T0-50.369 to T0-47.257. No significant
detections
are found in the 15-350 keV images created using this event data interval.

BAT retains decreased, but significant, sensitivity to rate increases for
gamma-ray events outside of its FOV. About 76.67% 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 than those
within the FOV.

The results of the BAT analysis are available at
https://swift.gsfc.nasa.gov/results/BATbursts/team_web/S190901ap/web/source_public.html

GCN Circular 25618

Subject
LIGO/Virgo S190901ap : GRAWITA spectroscopic observation of candidate ZTFabvizsw
Date
2019-09-02T23:07:12Z (6 years ago)
From
Lina Tomasella at INAF,Padova <lina.tomasella@inaf.it>
I. Salmaso, L. Tomasella, S. Benetti (INAF Padova), P. D���Avanzo (INAF Brera), E. Cappellaro (INAF Padova), M.T. Botticella (INAF Napoli), R. Martone (Ferrara University), A. Rossi (INAF Bologna), E. Brocato (INAF Teramo), on behalf of GRAWITA report:


We used the Asiago 1.82m Copernico telescope equipped with the AFOSC spectrograph and camera to observe one of the candidate transient found by the Zwicky Transient Facility (ZTFabvizsw; Kool et al. GCN 25616) localized in the region of the gravitational wave trigger S190901ap (LVC et al. GCN 25606, GCN 25614). 

Optical images were obtained with the uBVgriz filters. Two optical spectra (1800s, 2400s exposure time) were obtained using the grism gr4 (wavelength range ~ 340-820 nm, resolution 1.4 nm). The spectrum is typical of a Galactic K or M star. Thus it could be a Galactic variable, although a rarer case of stellar microlensing event could not be excluded (see Benetti et al. 1995, Astron. Astrophys. Letters, 294, L37).

GCN Circular 25619

Subject
LIGO/Virgo S190901ap : GRAWITA spectroscopic observation of candidate ZTFabvixoy
Date
2019-09-03T00:36:22Z (6 years ago)
From
Lina Tomasella at INAF,Padova <lina.tomasella@inaf.it>
I. Salmaso, L. Tomasella, S. Benetti (INAF Padova), P. D���Avanzo (INAF Brera), E. Cappellaro (INAF Padova), M.T. Botticella (INAF Napoli), R. Martone (Ferrara University), A. Rossi (INAF Bologna), E. Brocato (INAF Teramo), on behalf of GRAWITA report:


We used the Asiago 1.82m Copernico telescope equipped with the AFOSC spectrograph and camera to observe the candidate transient found by the Zwicky Transient Facility ZTFabvixoy (Kool et al. GCN 25616) localized in the region of the gravitational wave trigger S190901ap (LVC et al. GCN 25606, GCN 25614). 

The optical spectrum (2700s exposure time) was obtained using the grism gr4 (wavelength range ~ 340-820 nm, resolution 1.4 nm) and it is characterized by a strong blue continuum. There is a weak Halpha emission,  at rest wavelength, surrounded by broad absorption troughs. The emission core inside Hbeta and Hgamma absorption is only perceptible, while higher Balmer lines are in pure absorption. The object is likely a CV.

GCN Circular 25620

Subject
LIGO/Virgo S190901ap: Hobby-Eberly Telescope VIRUS observations of target galaxy; no obvious optical counterpart.
Date
2019-09-03T00:41:40Z (6 years ago)
From
J. Craig Wheeler at U.Texas Austin <wheel@astro.as.utexas.edu>
M. J. B. Rosell, Sergey Rostopchin and Aaron Zimmerman, on behalf of the LIGO Hobby-Eberly Telescope Response (LIGHETR) team, report the spectroscopic observation of the field of S190901ap (GCN #24208) with the VIRUS IFU array. We took observations on our most likely target within a list of 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. The field is 50x50 arc seconds. We observed the galaxy:

GW65.490150+1.838955 04:21:57.636 +01:50:20.24
A more detailed report of the results will be submitted later.

GCN Circular 25622

Subject
LIGO/Virgo S190901ap: Hobby-Eberly Telescope VIRUS observations of ZTF19abvionh
Date
2019-09-03T05:05:39Z (6 years ago)
From
J. Craig Wheeler at U.Texas Austin <wheel@astro.as.utexas.edu>
M. J. B. Rosell, Karl Gebhardt, Aaron Zimmerman, Matthew Shetrone, Chris Fryer, J. Craig Wheeler, Steve Odewahn, and Nathan McReynolds on behalf of the LIGO Hobby-Eberly Telescope Response (LIGHETR) team, report the spectroscopic observation of the candidate optical transient ZTF19abvionh(GCN #25616) in the field of S190901ap (GCN #24208). The observations cover the wavelength range of 3500 to 5500 Angstroms. We detect a nearly featureless continuum peaking at about 4500 Angstroms. There are emission lines at about 4124 Angstroms and 5370 Angstroms that probably correspond to [O II] 3727 and Hbeta at a redshift of ~0.1. These emission lines are likely to be associated with nearby galaxy GALEXASC J165500.03+140301.3. The image of the target object falls within the extent of this galaxy. The distance corresponding to this redshift is 450 Mpc, about 2.5 sigma more than the estimated distance of the merger candidate.

GCN Circular 25624

Subject
LIGO/Virgo S190901ap: Hobby-Eberly Telescope VIRUS observations of ZTF19abvionh [correction on the peak]
Date
2019-09-03T05:50:14Z (6 years ago)
From
Maria Jose Bustamante Rosell at UT Austin <majoburo@utexas.edu>
M. J. B. Rosell, Karl Gebhardt, Aaron Zimmerman, Matthew Shetrone, Chris
Fryer, J. Craig Wheeler, Steve Odewahn, and Nathan McReynolds on behalf of
the LIGO Hobby-Eberly Telescope Response (LIGHETR) team.
After further calibrations, we report the nearly featureless spectrum
reported in GCN CIRCULAR 25620 does not peak at about 4500 A but further in
the blue, rising towards 3500 A, the limit of our wavelength range.

GCN Circular 25625

Subject
LIGO/Virgo S190901ap: No counterpart candidates in Fermi-LAT observations
Date
2019-09-03T07:30:15Z (6 years ago)
From
Magnus Axelsson at Stockholm U. <magaxe@kth.se>
M. Axelsson (KTH and Stockholm Univ.), F. Piron (CNRS/IN2P3/LUPM), L. Scotton (University and INFN, Torino), F. Longo (University and INFN, Trieste) and E. Bissaldi (Politecnico and INFN Bari) report on behalf of the Fermi-LAT Collaboration:

We have searched data collected by the Fermi Large Area Telescope (LAT) on Sep 1, 2019, for possible high-energy (E > 100 MeV) gamma-ray emission in spatial/temporal coincidence with the LIGO/Virgo trigger S190901ap (GCN 25606).

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 time, and "cumulative coverage" as the integral of the instantaneous coverage over time. Fermi-LAT had instantaneous coverage of 37% of the LIGO probability region at the time of the trigger (T0 = 2019-09-01 23:31:01.838 UTC), and reached 98% cumulative coverage after ~5 ks. The remaining area was not observed within 10 ks following 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. No significant sources were found.

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 1 GeV for this search vary between 5E-08 and 3E-07 [erg/cm^2/s].

The Fermi-LAT point of contact for this event is Lorenzo Scotton (lorenzo.scotton@to.infn.it<mailto:lorenzo.scotton@to.infn.it>).

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.

GCN Circular 25626

Subject
LIGO/Virgo S190901ap: No neutrino candidates at Pierre Auger Observatory
Date
2019-09-03T09:00:45Z (6 years ago)
From
Jaime Alvarez-Muniz at Pierre Auger Observatory <jaime.alvarezmuniz@gmail.com>
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 S190901ap
T0=2019-09-01 23:31:01 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 S1900901ap as well as 1 day after it.

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

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 (38.7%) with
the LIGO/Virgo 90% localization region (LALInference.v2.fits.gz)
at the time T0 of the merger alert, achieving MAXIMUM OVERLAP (47.7%)
at approximately T0+17.2 hours

-------
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
https://arxiv.org/abs/1906.07422

GCN Circular 25630

Subject
LIGO/Virgo S190901ap: Upper limits from AGILE-GRID observations
Date
2019-09-03T14:32:13Z (6 years ago)
From
Martina Cardillo at INAF-IAPS <martina.cardillo@inaf.it>
M. Cardillo (INAF/IAPS), F. Verrecchia (SSDC,and INAF/OAR), F. Longo 
(Univ. Trieste,
and INFN Trieste),C. Pittori, F. Lucarelli (SSDC, and INAF/OAR), M. 
Tavani (INAF/IAPS
and Univ. Roma Tor Vergata),C. Casentini, G. Piano, A. Ursi 
(INAF/IAPS),A. Bulgarelli,
V. Fioretti,N. Parmiggiani (INAF/OAS-Bologna), M. Pilia (INAF/OA-Cagliari),
report on behalf of the AGILE Team:

In response to the LIGO-Virgo GW event S190901ap at T0 = 2019-09-01 
23:31:01.838
UTC a preliminary analysis of the AGILE exposure at T0 shows that the 
Gamma-Ray
Imaging Detector (GRID) exposure covered about 20% of the 90% c.l. 
localization
region (LR) (13% of 90% c.l. localization region (LR) is occulted by Earth).

We performed an analysis of the GRID data in the energy range 50 MeV -
10 GeV on T0, where good exposure of the S190901ap 90% c.l. LR was 
available.
No candidate gamma-ray transient was detected.

The following preliminary GRID values of 3-sigma upper limit (UL) are 
obtained:

from 3.00e-07 to 9.32e-06 erg cm^-2 s^-1, with exposure of about 16% of 
the LR over
the time interval ( T0s ; T0 + 10s );
from 3.59e-08 to 6.91e-06 erg cm^-2 s^-1, with exposure of about 26% of 
the LR over
the time interval ( T0s ; T0 + 100s );

These measurements were obtained with AGILE observing a large portion of
the sky in spinning mode. Additional analysis of AGILE data is in progress.

GCN Circular 25632

Subject
LIGO/Virgo S190901ap: GROWTH-India follow-up of ZTF19abvionh
Date
2019-09-03T16:40:09Z (6 years ago)
From
Gaurav Waratkar at IIT Bombay <gauravwaratkar24@gmail.com>
Harsh Kumar (IITB), Anirban Dutta (IIA), Gaurav Waratkar (IITB), Kunal
Deshmukh (IITB), Maitreya Khandagale (IITB), Avinash Singh (IIA), Erik Kool
(OKC), Varun Bhalerao (IITB), G. C. Anupama (IIA), Urgain Stanzin (IIA)
report on behalf of the GROWTH collaboration:

We observed the optical counterpart candidate ZTF19abvionh (Erik Kool et
al. GCN 25616, M. J. B. Rosell et al. GCN 25622, GCN 25624) of the
gravitational
wave trigger S190901ap (LVC et al. GCN 25606, GCN 25614) with the 0.7m
GROWTH-India telescope. We obtained a series of exposures, each 600 sec
long, in SDSS-r filter starting from 2458729.15950926 JD. We used PS1
catalog images for image subtraction. The candidate was clearly detected in
the subtracted images. Photometry of the subtracted images is reported
below:

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

JD(Start) | Name | Filter | Mag | Mar_err|

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

2458729.15950926 | ZTF19abvionh | r | 20.81 | 0.117

2458729.16622148 | ZTF19abvionh | r | 20.83 | 0.088

2458729.20642199 | ZTF19abvionh | r | 20.56 | 0.108

2458729.21345010 | ZTF19abvionh | r | 20.50 | 0.088

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

Our measurements indicate a rise in the r-band brightness of the candidate.
Further observations are planned. We encourage further monitoring of this
candidate.


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).

GCN Circular 25634

Subject
LIGO/Virgo S190901ap: Additional observations from the Zwicky Transient Facility
Date
2019-09-03T19:26:03Z (6 years ago)
From
Robert Stein at DESY <robert.stein@desy.de>
Robert Stein (DESY), Erik Kool (OKC), Viraj Karambelkar (Caltech), Mansi Kasliwal (Caltech), Daniel Perley (LJMU), Shreya Anand (Caltech), Michael Coughlin (Caltech), Yashvi Sharma (Caltech), Leo P. Singer (NASA GSFC), Igor Andreoni (Caltech), Gaurav Waratkar (IITB), Harsh Kumar (IITB), Maitreya Khandagale (IITB), Kunal Deshmukh (IITB), Varun Bhalerao (IITB), G. C. Anupama (IIA), Dougal Dobie (USyd/CSIRO), Brad Cenko (NASA GSFC), Tomas Ahmuda (UMD), Eric Bellm (UW), Albert Kong (NTHU), Anna Franckowiak (DESY), Pradip Gatkine (UMD)

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

We again observed the localization region of the gravitational wave trigger S190901ap (LVC et al. GCN 25606, GCN 25614) with the Palomar 48-inch telescope equipped with the 47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019). The tiling was optimally determined and triggered using the GROWTH Target of Opportunity marshal (Coughlin et al. 2019a, Kasliwal et al. 2019b). We started our new target-of-opportunity observations in the g-band and r-band beginning at UT 2019-09-03 03:12 UT. Each exposure was 30s, and due to poor weather images had a typical median depth of 19.5 mag. Moreover, the planned observations were not completed due to dome closure. Between the two nights of observations, we have covered 48% of the enclosed probability based at least once, and 35% of the enclosed probability at least twice. 

The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC to search for potential counterparts (Masci et al. 2019). AMPEL (Nordin et al. 2019) was used to search the alerts database for candidates. We rejected stellar sources (Tachibana and Miller 2018) and moving objects and applying machine learning algorithms (Mahabal et al. 2019), and removed candidates with history of variability prior to the merger time. One additional object was found by our pipeline, detected twice on our first night of observations (Kool et al. GCN 25616).
 
------------------------------------------------------------------------
ZTF Name     | RA (deg) | DEC (deg)  | Filter | Mag | Magerr
------------------------------------------------------------------------
ZTF19abvitlr | 279.200304 | -11.579390 | r      | 18.89 | 0.08
------------------------------------------------------------------------
 
ZTF19abvitlr is a red transient located in a crowded stellar field at galactic latitude of -2 deg, and was not detected in observations on Aug 30 to a depth of 20.1 mag. It is significantly offset from the nearest PS1 source, and has a steep lightcurve rise. Given these properties it is likely a reddened galactic Cataclysmic Variable. Spectroscopic follow-up would confirm the nature of this transient.
 
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; SDSU, 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 database searches are done by AMPEL (Nordin et al. 2019). Alert filtering and follow-up co-ordination is being undertaken by the GROWTH marshal system (Kasliwal et al. 2019).

GCN Circular 25638

Subject
LIGO/Virgo S190901ap: Keck I LRIS spectroscopy of ZTF19abvionh
Date
2019-09-04T00:26:12Z (6 years ago)
From
Mansi M. Kasliwal at Caltech/Carnegie <mansikasliwal@gmail.com>
Kevin Burdge (Caltech), Mansi M. Kasliwal (Caltech), Daniel A. Perley (LJMU)

report on behalf of the GROWTH collaboration

We obtained a Keck I LRIS spectrum of ZTF19abvionh (Kool et al. GCN 25616).
We see a hot, blue continuum and host galaxy lines at z=0.0985. The
corresponding luminosity distance of 456 Mpc is inconsistent with the GW
constraints on S190901ap (LVC et al. GCN 25614, GCN 25606) suggesting this
could evolve into a young supernova. Our conclusions are broadly consistent
with Rossell et al. GCN 25622.

GCN Circular 25639

Subject
LIGO/Virgo S190901ap: Keck I LRIS spectroscopy of ZTF19abvizsw
Date
2019-09-04T00:27:15Z (6 years ago)
From
Mansi M. Kasliwal at Caltech/Carnegie <mansikasliwal@gmail.com>
Kevin Burdge (Caltech), Daniel A. Perley (LJMU) and Mansi M. Kasliwal
(Caltech) report on behalf of the GROWTH collaboration:

We obtained a Keck I LRIS spectrum of ZTF19abvizsw (Kool et al. GCN
25616).  The reduced spectrum shows a featureless continuum superimposed
with a number of narrow absorption lines, including Mg II, Mg I, and Fe II
at a consistent redshift of z=1.26.

This is far beyond the GW distance constraints on S190901ap (LVC et al. GCN
25614, GCN 25606) and demonstrates that this source is unrelated to the
LIGO/Virgo source.  It could be a flaring AGN or blazar, but there is no
counterpart in PS1 or WISE and only a dim, marginal object at this location
in the Legacy Survey.  It may also be a GRB afterglow.

Our conclusions disagree with those of Salmaso et al. (GCN 25618), who
reported an M- or K-dwarf spectrum for this object.  We note that there is
a bright, red star less than 2 arcsec away from the transient position and
it is possible that the spectrum reported in GCN 25618 may correspond to
that object.

GCN Circular 25640

Subject
LIGO/Virgo S190901ap : SVOM/GWAC-F60A observation of transient ZTFabvizsw
Date
2019-09-04T01:42:35Z (6 years ago)
From
Liping Xin at NAOC, SVOM <xlp@nao.cas.cn>
J. Y. Wei (NAOC), L. P. Xin (NAOC), S. Antier (CNRS/APC), J. Wang (GXU),
N. Leroy (CNRS/LCL), D. Turpin (NAOC)

on behalf of the SVOM Multi Messenger Astronomy and GWAC teams:
http://www.svom.fr/en/svom-mma-and-gwac-team

We used the 60cm SVOM/GWAC-F60A telescope to observe the transient found
by the Zwicky Transient Facility ZTF19abvizsw (Kool et al. GCN 25616)
localized in the region of the gravitational wave trigger S190901ap
(LVC et al. GCN 25606, GCN 25614) during 17:28:07 and 18:45:07 UT on 02th,
Sep. 2019.  

After stacking the images for 31*150 sec, the source was detected with a
brightness of R=20.53+/-0.16 mag calibrated by nearby USNO R2 magnitudes.
Comparing with the reported by Kool et al., GCN 25616, the source was
fading for about one magnitude. 

Considering its fast decay, a featureless  continuum superimposed 
with a number of narrow absorption lines and the large distance of z=1.26
(Burdge et al., GCN 25639), it is possible an orphan GRB afterglow.

The stacked image observed by GWAC-F60A is shown here,
http://cmm.svom.cn/gwpub/O3/S190901ap/ZTF19abvizsw_F60_findingchart.png
(user:svomo3 pwd:gwo3)

SVOM/GWAC-F60A is a dedicated telescope for  follow-ups of SVOM/GWAC
system, and is operated by Guangxi university and NAOC, CAS, at Xinglong
observatory, China.

GCN Circular 25645

Subject
LIGO/Virgo S190901ap: Upper limits from Insight-HXMT/HE observations
Date
2019-09-04T06:25:45Z (6 years ago)
From
Ce Cai at IHEP <caice@ihep.ac.cn>
J. M. Yao, Y. G. Zheng, C. Cai, Q. Luo, S. Xiao, Q. B. Yi, 
Y. Huang, C. K. Li, G. Li, X. B. 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 reported LIGO/Virgo 
S190901ap event (GCN #25606), trigger time 2019-09-01T23:31:01.838 UTC. 
At T0, about 61% of the LIGO localization region was covered by the 
Insight-HXMT without occultationby 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 center 
of the LIGO-Virgo location probability map (RA=57 deg, DEC=-21 deg), 
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):
1 s:   7.7e-08 erg cm^-2
10 s:  1.3e-07 erg cm^-2

Band model 2 (alpha=-1.0, beta=-2.3, Ep=230 keV):
1 s:   1.4e-07 erg cm^-2
10 s:  2.7e-07 erg cm^-2

Band model 3 (alpha=-0.0, beta=-1.5, Ep=1000 keV):
1 s:   3.7e-07 erg cm^-2
10 s:  2.9e-06 erg cm^-2

All measurements above are made with the CsI detectors operating in the
regular mode with the energy range of about 80-800 keV (deposited 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 spacecraft.

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.

GCN Circular 25647

Subject
LIGO/Virgo S190901ap: Upper limits from CALET observations.
Date
2019-09-04T07:06:55Z (6 years ago)
From
Yuta Kawakubo at Louisiana State U./CALET <kawakubo1@lsu.edu>
N. Cannady (GSFC/UMBC), A. Yoshida, T. Sakamoto, V. Pal'shin, 
S. Sugita (AGU), Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), 
S. Nakahira (RIKEN), Y. Asaoka, S. Torii (Waseda U),
Y. Shimizu, T. Tamura (Kanagawa U), M. L. Cherry (LSU), 
S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena),
and the CALET collaboration:

The CALET Gamma-ray Burst Monitor (CGBM) was operating at the trigger 
time of S190901ap T0 = 2019-09-01 23:31:01.838 UT (The LIGO Scientific
Collaboration and Virgo Collaboration, GCN Circ. 25606 and 25614).

No CGBM on-board trigger occurred around the event time.  Based
on the LIGO-Virgo localization sky map, the summed LIGO probabilities 
inside the CGBM HXM (7 - 3000 keV) and SGM (40 keV - 28 MeV) fields 
of view are 6 % and 61 %, respectively (and 82 % credible region 
of the updated localization map was above the horizon).  The HXM and 
SGM fields of view were centered at RA = 345.1 deg, Dec = 22.4 deg
and RA = 353.8 deg, Dec = 16.7 deg at T0, respectively.

Based on the analysis of the light curve data with 0.125 sec
time resolution from T0-60 sec to T0+60 sec, we found no
significant excess (signal-to-noise ratio >= 7) around the trigger
time in either the HXM or the SGM data.

The CALET Calorimeter (CAL) was operating in the low energy trigger
mode at the trigger time of S190901ap. Using the CAL data, we have 
searched for gamma-ray events in the 1-10 GeV band from -60 sec 
to +60 sec from the GW trigger time and found no candidates 
in the overwrap region with the LIGO-Virgo probability map. 
The 90% upper limit of CAL is 6.3x10^-5 erg/cm^2/s (1-10 GeV) when
the summed LIGO-Virgo probability reaches 5%.
The CAL FOV was centered at RA= 353.8 deg, Dec= 16.6 deg at T0.

GCN Circular 25648

Subject
LIGO/Virgo S190901ap: no counterpart candidate in the SVOM/GWAC observations
Date
2019-09-04T08:21:17Z (6 years ago)
From
Xuhui Han at NAOC/SVOM <hxh@nao.cas.cn>
J. Y. Wei (NAOC), X. H. Han (NAOC), S. Antier (CNRS/APC), J. Wang (GXU),
N. Leroy (CNRS/LCL), L. P. Xin (NAOC)

on behalf of the SVOM Multi Messenger Astronomy and GWAC teams:
http://www.svom.fr/en/svom-mma-and-gwac-team

We observed 23 sky regions (total: 3450 square degrees with overlaps)
to cover the skymap of the advanced LIGO/Virgo trigger S190901ap,
with SVOM/GWAC, at Xinglong Observatory equipped with a set of two
types of wide angle cameras: FFOV cameras (FOV~900 square degrees/camera,
aperture = 3.5 cm) and JFOV cameras (FOV~150 square degrees/camera,
aperture = 18 cm). SVOM/GWAC currently comprises 4 FFOV cameras and
16 JFOV cameras, working with unfiltered band. The observations are
operated in time-series mode, taking one exposure every 25 seconds
(20s exposure + 5s readout). We estimate a 21.1% prior 
probability that the 23 observed and processed regions contain 
the true location of the source. The images were taken between ~12
hours and ~21 hours after the event trigger time.

The coordinates of the 23 sky regions and observation times are listed
below:

No. Ra  Dec start-obs(UTC)  end-obs(UTC)    Camera_TYPE

1 14:52:45.36 36:27:42.12  2019-09-02 11:50:35 2019-09-02 12:57:50 JFOV
2 14:47:05.52 48:27:28.80  2019-09-02 12:52:10 2019-09-02 12:57:50 JFOV
3 16:04:10.80 30:49:03.00  2019-09-02 11:41:44 2019-09-02 11:47:24 JFOV
4 15:09:00.24 18:30:39.60  2019-09-02 11:50:38 2019-09-02 11:54:17 JFOV
5 15:07:09.12 30:35:42.36  2019-09-02 11:50:39 2019-09-02 11:54:17 JFOV
6 15:26:18.24 15:16:59.88  2019-09-02 13:08:45 2019-09-02 13:26:57 JFOV
7 16:02:03.12 35:25:58.44  2019-09-02 13:05:29 2019-09-02 13:21:17 JFOV
8 16:39:42.96 27:17:34.80  2019-09-02 12:08:56 2019-09-02 12:23:06 JFOV
9  01:16:21.62 -15:31:53.40 2019-09-02 16:24:34 2019-09-02 16:52:31 JFOV
10 17:19:00.24 52:14:09.60  2019-09-02 14:45:41 2019-09-02 14:56:13 JFOV
11 18:05:18.24 01:30:15.52  2019-09-02 13:51:32 2019-09-02 13:52:21 JFOV
12  02:28:14.83 -15:30:36.00 2019-09-02 17:27:23 2019-09-02 19:01:31 JFOV
13  03:19:23.62 -3:14:21.77  2019-09-02 17:31:26 2019-09-02 17:52:54 JFOV
14  03:58:00.72 -1:57:11.38  2019-09-02 17:34:35 2019-09-02 17:49:09 JFOV
15  03:41:15.24 01:27:46.30  2019-09-02 18:01:48 2019-09-02 18:22:04 JFOV
16  04:31:50.62 13:46:42.60  2019-09-02 18:01:48 2019-09-02 18:14:22 JFOV
17  04:08:53.54 15:03:23.04  2019-09-02 16:59:48 2019-09-02 20:27:27 JFOV
18  04:44:53.30 35:53:54.24  2019-09-02 18:04:30 2019-09-02 18:21:05 JFOV
19  04:53:17.66 01:30:11.16  2019-09-02 19:14:43 2019-09-02 20:04:18 JFOV
20  05:43:52.15 13:49:17.40  2019-09-02 19:22:00 2019-09-02 19:53:46 JFOV
21  04:52:20.66 -15:27:02.16 2019-09-02 20:16:15 2019-09-02 20:35:42 JFOV
22  05:43:23.81 -3:10:38.86  2019-09-02 20:26:22 2019-09-02 20:35:42 JFOV
23  05:24:02.42 14:49:40.80  2019-09-02 18:40:24 2019-09-02 18:52:32 JFOV

The sky coverage map is available at: 
http://cmm.svom.cn/gwpub/O3/S190901ap/S190901ap.png 
(user:svomo3 pwd:gwo3)

The weather condition was clear during the observations. A 3 sigma 
limiting magnitude of about 16.3 mag in R band was obtained in the single 
frames. No credible new source is detected by our online pipeline during 
follow-up observations. A more detailed image analysis including
co-addition is ongoing with our offline pipeline to search for transient
candidates.

GCN Circular 25649

Subject
LIGO/Virgo S190901ap: MASTER OT J171434.95+280725.6/AT2019pjv detection
Date
2019-09-04T08:42:33Z (6 years ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
V. Lipunov, T.Pogrosheva, E. Gorbovskoy, F.Balakin,  V.Kornilov, N.Tyurina, P.Balanutsa,A.Kuznetsov, V.Vladimirov, D. Vlasenko,
I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,  D.Kuvshinov, A.Chasovnikov,V.Topolev,
A.Posdnyakov(Lomonosov Moscow State University, SAI, Physics Department),
R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias),
V. Yurkov, A. Gabovich, Yu. Sergienko (Blagoveschensk Educational State University)
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA),
H.Levato (Instituto de Ciencias Astronomicas, de la Tierra y del Espacio ICATE),
D. Buckley (South African Astronomical Observatory),
O.A. Gres, N.M. Budnev, O.Ershova (Irkutsk State University, API),

MASTER Global Robotic Net ( http://observ.pereplet.ru, Lipunov et al., 2010,
Advances in Astronomy, vol. 2010, 30L)
started LIGO/Virgo S190901ap error-box (LVC GCN 25606) alert and inspect 
observations at 2019-09-02 01:42:16 UT (Lipunov et al GCN 25609).

During inspection we found OT, that can be assotiated  with known 
PGC059913 (distance ~ 100Mpc, Btot=15.7), see image.
OT offset are 44W 10.8N arcsec.


  MASTER OT J171434.95+280725.6 discovery - possibly LVC S190901ap optical 
counterpart.

MASTER-IAC auto-detection system discovered OT source at
(RA, Dec) = 17h 14m 34.95s +28d 07m 25.6s on 2019-09-03.97890 UT.

The OT unfiltered magnitude is 18.9m (limit 19.7m).

The OT is seen in 2 inspect images. There is no minor planet at this place.

We have reference image without OT on 2015-09-15.93950 UT with unfiltered magnitude limit 20.4m.

Spectral observations are required.

The discovery and reference images are available at:
http://master.sai.msu.ru/static/OT/171434.95280725.6.png

This OT is in TNS as AT2019pjv

GCN Circular 25650

Subject
LIGO/Virgo S190901ap : GRAWITA photometric observation of candidate ZTFabvizsw and GCN 25618 revision
Date
2019-09-04T08:57:51Z (6 years ago)
From
Lina Tomasella at INAF,Padova <lina.tomasella@inaf.it>
I. Salmaso, L. Tomasella, S. Benetti (INAF Padova), P. D���Avanzo (INAF Brera), E. Cappellaro (INAF Padova), M.T. Botticella (INAF Napoli), R. Martone (Ferrara University), A. Rossi (INAF Bologna), E. Brocato (INAF Teramo), on behalf of GRAWITA report:

Following Burdge et al. (GCN 25639) we revised our results published in Salmaso et al. (GCN 25618). The average seeing of Salmaso et al. frames was around 2.5-3 arcsec and ZTF19abvizsw was barely visible in a single 60 sec long exposure, while a nearby brighter star (at R.A.= 18:37:53.50, decl=+61:29:45.96) had a magnitude g=19.52+/-0.04 close to that reported by Kool et al. in GCN 25616 for ZTF19abvizsw. Therefore we indeed took erroneously the spectrum of the nearby star which is clearly unrelated to the gravitational wave trigger S190901ap.
ZTF19abvizsw stands clearly out in our best seeing frames and the preliminary magnitudes we measure are the following (Time gives the UT start):
Time (UT)               filter  mag(AB) err
���������������������������������������������������
2019-09-02 20:56:48  g   20.77     0.11
2019-09-02 20:57:58  r    20.54    0.12
2019-09-02 20:59:07  i     20.25    0.15
2019-09-02 21:00:17  z    20.65    0.15
The transient is fading rapidly in agreement with the finding of Perley et al. (CGN 25643).
We regret for any trouble this may have caused.

GCN Circular 25653

Subject
LIGO/Virgo S190901ap: GTC follow-up spectroscopic observations of ZTF19abvizsw
Date
2019-09-04T11:44:44Z (6 years ago)
From
Peter Jonker at SRON/RU <p.jonker@sron.nl>
A.J. Levan (Radboud), P.G. Jonker (SRON/Radboud), P. Rodriguez Gil, M.A.P.
Torres (IAC/ULL), K. Maguire (TCD), M. Fraser (UCD), D. Mata (JBCA, University
of Manchester) report on behalf of a larger collaboration:

We obtained 3x900 sec of spectroscopic observations of ZTF19abvizsw with the GTC on La Palma on 2
September 2019 over the time interval 20:37 - 22:05 UT  using the R1000R grating and the OSIRIS
instrument. The spectra cover the range 5100-10000 AA. A strong continuum is detected with
prominent absorption lines which we identify as FeII (2344, 2374, 2383, 2586, 2600 AA) and MgII
(2796, 2803 AA) and MgI (2852 AA) at a common redshift of z=1.258. This is in agreement with the
results of Burdge et al. (GCN 25639). Indeed the spectral features provide a good match to the
composite spectra of GRB afterglows (Christensen et al. 2011).  This offers further support for
the identification of ZTF19abvizsw as an untriggered GRB (Perley et al. GCN 25643). Searches in
existing gamma-ray observations around the rise time would be strongly merited. 


We thank the GTC staff and especially Peter Pessev for their assistance in
acquiring these observations.

Acknowledgements: PGJ acknowledges support from the European Research
Council under ERC Consolidator Grant agreement no 647208.

GCN Circular 25654

Subject
LIGO/Virgo S190901ap: GOTO optical coverage and detection of AT2019pjv
Date
2019-09-04T13:39:34Z (6 years ago)
From
Danny Steeghs at U.of Warwick/GOTO <dsteeghs@gmail.com>
K.Ackley(2), D.Mata-Sanchez(8), Y-L.Mong(2), R.Cutter(1),
K.Ulaczyk(1), J.Lyman(1), D.Steeghs(1), G.Ramsay(5),
D.Galloway(2), L.Makrygianni(3), M.Kennedy(8), A.Obradovic(2),
M.Dyer(3), V.Dhillon(3), P.O'Brien(4), D.Pollacco(1),
E.Thrane(2), S.Poshyachinda(6), E.Palle(7), K.Wiersema(1),
T. Marsh(1), R.West(1), B.Gompertz(1), E.Stanway(1),
A.Casey(2), M.Brown(2), E.Rol(2), J.Mullaney(3), S.Littlefair(3),
E.Daw(3), J.Maund(3), R.Starling(4), R.Eyles(4), S.Tooke(4),
U.Sawangwit(6), D.Mkrtichian(6), S.Awiphan(6), S.Aukkaravittayapun(6),
P.Irawati(6), R.Breton(8), T.Heikkila(9),
R.Kotak(9), L.Nuttall (10)

(1) Warwick University; (2) Monash University; (3) Univ. of Sheffield;
(4) University of Leicester; (5) Armagh Observatory & Planetarium;
(6) National Astronomical Research Institute of Thailand;
(7) Instituto de Astrofisica de Canarias; (8) Univ. of Manchester;
(9) University of Turku; (10) University of Portsmouth


report on behalf of the GOTO collaboration:

We report on observations with the Gravitational-wave Optical
Transient Observer (GOTO) on La Palma, Canary Islands, in response to
the LIGO/Virgo gravitational wave event  S190901ap, triggered
2019-09-01 23:31:01.838 UTC (GCN #25606).   We performed a series of
3x60s exposures using a wide (400-700nm passband) L-band filter with a
typical 5-sigma photometric depth equivalent to g~20 based on a
photometric calibration against PS1 sources.

Observations commenced on 2019-09-01 23:37:46 UT (6.7 min
post-trigger) and continued  through 2019-09-04 05:45:10 UT. In total
we covered 2507 square degrees containing ~28.2% of the total source
location probability (based on the skymap at
https://gracedb.ligo.org/api/superevents/S190901ap/files/bayestar.fits
.gz) across 162 tiles. The median number of visits per tile was 3,
with some tiles visited up to 18 times.

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, which were available for 88% of our tiles. Source
candidates were initially filtered using a trained classifier and
cross-matched against a variety of catalogs, including the MPC and
PS1. Human candidate vetting was performed on those candidates
identified by the classifier. No additional viable optical counterpart
candidates beyond those already reported were identified.

We detected AT2019pjv (Lipunov et al. GCN #25649) as a rising
transient. The source rose above our detection limit on Sept 2nd, with
internal designation GOTO2019hope, and no source was detected at this
position during a series of observations preceding the GW event (most
recent visit pre-trigger 2019-08-06). We provide the following
preliminary magnitudes:

DATE:   MAG:

2019-08-06.9    >20
2019-09-01.9    > 20
2019-09-02.9    ~ 19.6
2019-09-03.9    19.0

=======
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)

GCN Circular 25656

Subject
LIGO/Virgo S190901ap: Additional candidates from the Zwicky Transient Facility
Date
2019-09-04T15:35:38Z (6 years ago)
From
Robert Stein at DESY <robert.stein@desy.de>
Robert Stein (DESY), Erik Kool (OKC), Harsh Kumar (IITB), Michael Coughlin (Caltech), Mansi Kasliwal (Caltech), Daniel Perley (LJMU), Shreya Anand (Caltech), Yashvi Sharma (Caltech), Viraj Karambelkar (Caltech), Leo P. Singer (NASA GSFC), Igor Andreoni (Caltech), Gaurav Waratkar (IITB), Maitreya Khandagale (IITB), Kunal Deshmukh (IITB), Varun Bhalerao (IITB), G. C. Anupama (IIA), Dougal Dobie (USyd/CSIRO), Brad Cenko (NASA GSFC), Tomas Ahmuda (UMD), Eric Bellm (UW), Albert Kong (NTHU), Anna Franckowiak (DESY), Pradip Gatkine (UMD)
On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations:

We again observed the localization region of the gravitational wave trigger S190901ap (LVC et al. GCN 25606, GCN 25614) with the Palomar 48-inch telescope equipped with the 47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019). The tiling was optimally determined and triggered using the GROWTH Target of Opportunity marshal (Coughlin et al. 2019a, Kasliwal et al. 2019b). We started our new target-of-opportunity observations in the g-band and r-band beginning at UT 2019-09-04 10:18 UT. Each exposure was 30s, with a typical median depth of 20.8 mag in g band and 20.6 mag in r band. Across the three nights of observations (Kool et al. GCN 25616, Stein et al. GCN 25634), we have covered 73% of the enclosed probability at least once, and 67% of the enclosed probability at least twice. This estimate does not account for chip gaps.

The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC to search for potential counterparts (Masci et al. 2019). AMPEL (Nordin et al. 2019) was used to search the alerts database for candidates. We rejected stellar sources (Tachibana and Miller 2018) and moving objects, applied machine learning algorithms (Mahabal et al. 2019), and removed candidates with history of variability prior to the merger time. Two additional candidates were found by our pipeline.
 
------------------------------------------------------------------------
ZTF Name     | RA (deg)   | DEC (deg)  | Filter | Mag   | Magerr
------------------------------------------------------------------------
ZTF19abwsmmd | 22.666409  | -19.712405 | r      | 20.08 | 0.22
ZTF19abwvals | 73.250555  | +12.693030 | r      | 19.83 | 0.19
------------------------------------------------------------------------
 
ZTF19abwsmmd has a blue color (g - r ~ -0.25) and is located in a compact host galaxy with a SDSS photo z of ~0.05, consistent with the merger distance. It was not detected in g band on Aug 30 UT to a depth of 20.4 mag. ZTF19abwvals is red (g - r ~ 0.5), located in a host galaxy with an SDSS photo-z of ~0.13. It was not detected in g band on Sep 1 UT to a depth of 20.64. We encourage spectroscopic and photometric observations to discern the nature of these candidates.
 
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; SDSU, 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 database searches are done by AMPEL (Nordin et al. 2019). Alert filtering and follow-up co-ordination is being undertaken by the GROWTH marshal system (Kasliwal et al. 2019).

GCN Circular 25659

Subject
LIGO/Virgo S190901ap: Dabancheng-0.5m optical observations of AT2019pjv
Date
2019-09-04T16:53:06Z (6 years ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
B.Y. Yu, D. Xu, Z.P. Zhu, T.M. Zhang, X. Zhou, H.J. Wang, C.Z. Cui, D.W. 
Fan, Y.F. Xu (NAOC), X. Gao (Urumqi No.1 Senior High School), Z.B. Zhang 
(XJTS), S. Yang (Stockholm U.), H.B. Zhao, B. Li (PMO), J.Z. Liu, H.B. 
Niu (XAO), J.R. Mao,
J.M. Bai (YNAO), report on behalf of the GWFUNC collaboration:

We observed the optical transient AT2019pjv, a candidate of the optical 
counterpart of LIGO/Virgo S2019091ap (MASTER, Lipunov et al. GCN #25649; 
GOTO, Ackley et al., GCN #25654), using the Half Meter Telescope (HMT) 
located at Dabancheng, Xinjiang, China. Observations started at 14:31:01 
UT on 2019-09-04, and 5x150 s unfiltered frames were obtained.

The OT is clearly detected in each exposure, and we got m(r) = 18.00 +/- 
0.05 mag in the stacked image, calibrated with nearby PanSTARRS field.

In comparison with previous MASTER and GOTO measurements, the OT has 
been rising since its detection on Sep 2. Such behaviour is much more 
consistent with a young supernova than an optical afterglow of a short 
GRB or a kilonova.

GCN Circular 25661

Subject
LIGO/Virgo S190901ap : GRAWITA spectroscopic observation of candidate MASTER OT J171434.95+280725.6
Date
2019-09-04T20:38:39Z (6 years ago)
From
Lina Tomasella at INAF,Padova <lina.tomasella@inaf.it>
V. Nascimbeni, I. Salmaso, L. Tomasella, S. Benetti (INAF Padova), P. D���Avanzo (INAF Brera), E. Cappellaro (INAF Padova), E. Brocato (INAF Teramo), on behalf of GRAWITA report:


Under the Asiago Transient Classification Program (Tomasella et al. 2014, AN, 335, 841), we observed the candidate transient found by MASTER-IAC auto-detection system (Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L), announced in Atel # 13076 and GCN 25649, which is localized in the region of the gravitational wave trigger S190901ap (LVC et al. GCN 25606, GCN 25614). 

The optical spectrum was obtained with the Copernico 1.82m telescope equipped with Afosc spectrograph and grism #4 (wavelength range ~ 340-820 nm, resolution 1.4 nm). The best match is with Type Ia-91T like SNe about one week before maximum light. The redshift, as derived from SNID (Blondin and Tonry 2007, ApJ, 666, 1024), is z = 0.024, linking the transient to the host galaxy MCG+05-41-001 (z = 0.023 derived from the galaxy spectrum in SDSS, DR10). The transient is thus unrelated to the GW trigger S190901ap.

GCN Circular 25663

Subject
LIGO/Virgo S190901ap: No counterpart candidates in KAIT observations
Date
2019-09-05T00:01:34Z (6 years ago)
From
Weikang Zheng at UC Berkeley <weikang@berkeley.edu>
Sergiy Vasylyev, Nachiket Girish, Thomas de Jaeger, Yukei Murakami,
Benjamin E. Stahl, Keto D. Zhang, James Sunseri, Shaunak Modak,
WeiKang Zheng, Andrew Hoffman, 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 90% region of the gravitational-wave
event S190901ap (GCN 25606; GCN 25614) detected by LIGO/Virgo. More
than one thousand galaxies were selected from the Glade catalog V1.0
(Dalya et al., 2018, MNRAS, 479, 2374; http://aquarius.elte.hu/glade/)
according to their priority score. KAIT observed 156 of them on
Sep. 02 UT starting at 3.8 hours after the trigger, and additional
143 on Sep. 03 UT starting at 1.37 days after the trigger, according
to their priority scores and elevation visibility, with each clear-filter
exposure time being 60 s. 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.

In addition, we took 7x180s clear band images of ZTF19abvizsw/AT2019pim
(Kool et al., GCN 25616), now considered as an unrelated GRB optical
afterglows candidate (Burdge et al., GCN 25639; Wei et al., GCN 25640;
Perley et al., GCN 25643; Salmaso et al., GCN 25650; Levan et al.,
GCN 25653; Becerra et al., GCN 25655; Ho et al., GCN 25658). We estimate
the clear band magnitude to be ~21.3 +/- 0.2 mag in our co-added image at
Sep. 04.23 UT, calibrated to PS1 catalog.

GladeID   UT(Sep02)  RA_J2000   Dec_J2000
-----------------------------------------------
G0194613  03:19:18  14:31:05.4346  +00:36:46.4688
G1875693  03:22:46  14:31:39.36    -00:17:11.94
G0603373  03:23:55  14:31:44.381   +00:48:42.7932
G1878039  03:25:04  14:32:14.88    +00:47:01.356
G1733195  03:26:14  14:32:41.52    +00:47:29.832
G0658315  03:27:23  14:32:48.7318  +02:04:41.9088
G0905344  03:28:32  14:32:53.1482  +01:32:24.414
G0740361  03:29:42  14:33:15.055   -00:49:28.992
G0663999  03:30:53  14:33:20.1562  +00:39:52.5492
G0307996  03:32:02  14:33:29.1614  +00:46:53.3316
G0757580  03:33:12  14:33:35.365   +00:54:26.3196
G0608391  03:34:23  14:33:36.7675  -01:05:05.6112
G0748622  03:35:32  14:33:44.8279  +00:47:42.3024
G0664011  03:36:42  14:33:57.2167  +00:35:10.8528
G0745915  03:37:53  14:34:09.0014  +01:37:00.8616
G1742502  03:39:07  14:34:13.92    +03:01:40.116
G0737461  03:40:16  14:34:23.7269  +02:23:31.038
G0783945  03:41:25  14:34:27.0667  +01:04:49.0404
G1278665  03:42:34  14:34:38.0712  +01:38:46.0392
G0756340  03:43:44  14:34:42.1363  +00:54:50.0364
G1742550  03:44:53  14:34:47.76    +02:02:28.536
G0713702  03:46:48  15:20:51.7932  -00:43:47.9316
G1224425  03:47:57  15:21:02.4096  -03:33:40.914
G0020414  03:49:07  15:21:08.7708  -07:20:45.6684
G1403147  03:50:16  15:21:15.9667  -10:11:20.67
G0838596  03:51:29  15:21:18.5669  -04:18:36.8172
G0917972  03:52:41  15:21:23.269   -12:04:38.2476
G0331855  03:53:50  15:21:33.2374  -08:49:50.6424
G1450425  03:54:59  15:21:34.6142  -08:04:07.6404
G1290735  03:56:09  15:21:48.6254  -06:14:40.0632
G0303133  03:57:18  15:22:05.8226  -05:28:59.1924
G0971203  03:58:29  15:23:07.3058  +01:25:40.9296
G1147715  03:59:43  15:23:59.0551  -10:49:57.8712
G0042791  04:00:54  15:24:16.7506  -05:46:36.102
G1109765  04:02:04  15:24:44.8205  -04:40:08.346
G1362904  04:03:13  15:25:47.7394  -06:52:10.0992
G0070527  04:04:22  15:25:51.7714  -01:53:01.3236
G1191119  04:05:33  15:26:42.9382  +00:13:14.7504
G1452726  04:06:44  15:27:11.8543  -08:35:42.1188
G0940632  04:07:53  15:27:14.6155  -04:44:00.51
G0936205  04:09:03  15:27:19.314   -05:19:06.5028
G1059447  04:10:14  15:28:06.6029  -11:12:38.5776
G0883642  04:11:25  15:29:02.5378  -05:34:13.152
G0928928  04:12:34  15:29:20.3357  -05:25:03.3528
G0906688  04:13:46  15:30:27.7735  -10:56:40.6788
G1388643  04:14:55  15:34:27.9749  -09:15:48.906
G0214088  04:16:06  15:34:42.9053  -04:14:22.6068
G1461463  04:17:18  15:35:15.2527  -09:24:21.5568
G1172917  04:18:27  15:36:50.2661  -06:06:55.4328
G0989502  04:19:36  15:37:52.2437  -07:12:55.4724
G0536188  04:20:48  15:24:40.177   -12:42:49.8276
G0566794  04:27:19  16:02:19.8449  +16:20:46.2552
G0395107  04:28:28  16:04:26.7298  +17:45:01.188
G0479641  04:29:38  16:05:44.5862  +16:12:11.8944
G0593543  04:30:47  16:06:22.8334  +19:46:40.2636
G0668634  04:31:56  16:06:42.0703  +16:19:11.154
G0657647  04:33:35  16:11:11.0083  +61:16:04.5444
G0627263  04:35:18  16:12:53.357   -21:37:24.0528
G0554714  04:36:44  16:13:04.9805  +30:54:05.994
G0684706  04:38:11  16:14:57.0154  +55:52:25.0428
G0789194  04:39:34  16:28:38.2764  +39:33:04.968
G0666910  04:40:54  16:32:57.2095  +50:24:05.1156
G0708649  04:42:20  16:34:25.4846  +21:32:27.0096
G0818453  04:43:46  16:43:23.1554  -24:52:47.0784
G0636473  04:45:10  16:45:26.4149  +18:12:30.3948
G0004443  04:46:33  16:49:03.6732  -17:38:45.3732
G0667530  04:47:42  16:49:21.0204  -17:38:40.326
G0628454  04:48:52  16:50:53.4228  -15:00:14.346
G0559558  04:50:01  16:52:07.7491  -17:03:13.518
G0609502  04:51:12  16:53:04.8559  -16:17:27.3552
G0788598  04:52:40  16:53:52.207   +39:45:36.9288
G0748918  04:54:05  16:54:08.7598  -07:38:07.314
G0613278  04:55:16  16:54:53.6462  -16:57:07.2756
G0771147  04:56:40  16:57:58.0994  +27:51:15.7248
G0644414  04:57:58  17:06:49.8048  +42:25:24.492
G0602659  04:59:23  17:10:50.4713  -06:30:43.0848
G0656855  05:00:33  17:11:14.9486  -05:21:58.3812
G0624001  05:01:42  17:12:33.2081  -05:35:26.7432
G0633958  05:02:55  17:18:54.0893  +08:26:26.9448
G1041639  05:04:19  17:20:15.6739  +39:15:37.8468
G0393771  05:05:44  17:21:28.9747  -07:09:55.9764
G0601575  05:06:55  17:21:45.4687  -00:47:43.2564
G0611033  05:08:10  17:23:05.3832  +12:41:43.512
G0686176  05:09:26  17:24:37.8295  -02:43:06.222
G0678938  05:10:35  17:27:40.6349  -06:41:02.238
G0585341  05:11:45  17:35:42.6854  -07:41:34.7424
G0707284  05:13:08  17:40:05.1636  +33:48:41.1012
G0710164  05:15:07  17:42:31.9702  +00:13:00.336
G1308107  05:16:19  17:42:50.2001  -09:43:26.5872
G0669959  05:17:43  17:45:14.4214  +38:54:57.7944
G1059666  05:19:01  17:48:43.2055  +24:39:07.3404
G0627653  05:20:19  17:50:35.0904  -01:39:06.3288
G0771881  05:21:43  17:52:41.8286  +29:50:19.3596
G0563085  05:23:01  17:55:27.9053  -00:01:52.5144
G0636803  05:24:20  17:56:20.2442  +26:21:59.58
G0638214  05:25:38  18:02:09.4776  +12:52:02.1504
G0754747  05:26:50  18:11:54.9024  +07:43:50.61
G1347890  05:27:59  18:12:50.4859  +07:30:08.928
G0794966  05:29:12  18:14:28.5058  +00:46:55.1928
G1856081  05:30:26  18:16:40.56    +15:17:56.04
G0233642  05:31:42  18:26:07.163   +03:01:37.5384
G0826631  05:32:55  18:28:01.4722  +16:07:32.7612
G0154905  05:34:20  18:52:14.1797  -23:16:18.21
G0691261  05:35:50  18:57:37.5     +38:00:32.202
G1849647  05:37:31  22:49:54.72    +11:36:29.592
G0010892  06:31:39  23:14:54.2578  -20:59:45.3408
G0706844  06:32:51  23:17:27.2242  -10:01:50.466
G0703575  06:35:09  23:18:52.5439  -10:15:33.5268
G0551567  06:36:21  23:21:14.1725  -21:14:09.8736
G0553140  06:37:30  23:22:00.9228  -23:30:24.6924
G0582772  06:38:41  23:22:35.2735  -13:05:38.8392
G0001180  06:39:51  23:24:06.9506  -11:51:38.6856
G0800782  06:41:00  23:29:56.6969  -12:29:05.7048
G0606247  06:42:09  23:30:23.7377  -12:04:45.5448
G0820960  06:43:23  23:32:31.3476  -24:00:18.5652
G0556216  06:44:32  23:37:06.9288  -20:27:47.0988
G0612966  06:45:41  23:40:45.9667  -20:30:31.5108
G0666486  06:46:55  23:41:52.6685  -08:38:53.7144
G0579080  06:48:08  23:45:31.3037  -20:58:49.8036
G0751781  06:51:36  23:48:54.7118  -16:32:28.2588
G1852091  06:52:43  23:48:56.88    -16:32:24.684
G0748482  06:53:53  23:54:20.9254  -17:18:21.0348
G0733653  06:55:02  23:56:47.7247  -16:30:34.5924
G0755443  06:56:12  23:58:40.525   -17:33:31.7124
G0755095  07:30:01  00:07:10.2658  -21:47:11.5008
G0559232  07:31:14  00:11:12.5945  -33:34:42.8016
G0555127  07:32:26  00:13:02.9052  -24:12:52.5024
G0587522  07:33:35  00:19:04.9488  -22:56:11.184
G0665013  07:34:47  00:19:09.3768  -24:31:23.2068
G0552516  07:35:57  00:22:38.9513  -24:07:36.9624
G0823492  07:37:08  00:31:49.3798  -26:43:13.926
G0740509  07:38:17  00:36:27.3996  -27:47:07.4472
G0708432  07:39:31  00:53:54.0602  -31:05:43.8432
G1641290  07:40:42  01:04:30.36    -33:39:15.768
G0762311  07:41:54  01:06:12.2227  -30:10:41.1744
G1641121  07:43:07  01:19:41.448   -33:06:29.556
G0783834  07:44:21  01:19:47.6698  -33:04:59.9808
G0595298  07:45:32  01:23:14.8567  -32:50:28.6008
G0629787  07:55:55  00:08:34.535   -33:51:29.9196
G0725300  07:57:04  00:09:35.5241  -32:16:36.5412
G0681282  07:58:16  00:14:33.5014  -24:42:09.7452
G0820749  07:59:25  00:20:42.0396  -23:16:58.2348
G0594514  08:00:36  00:44:15.959   -28:37:56.2728
G0589660  08:01:46  00:49:42.0413  -30:17:43.1736
G0601466  08:02:55  00:50:19.1225  -30:29:07.7928
G0697151  08:04:08  01:07:21.6086  -33:22:33.3912
G0671624  08:05:20  01:07:35.9945  -33:38:16.404
G0785220  08:06:31  01:12:09.409   -32:14:32.6148
G0783779  08:07:43  01:13:07.4479  -34:00:55.4544
G0657724  08:08:56  01:22:32.7113  -29:58:57.054
G0562220  08:11:21  01:38:28.5005  -33:36:28.9836
G0238284  08:12:35  01:38:59.6544  -28:34:20.478
G0791379  08:13:48  01:50:14.1576  -28:52:18.912
G0557460  08:15:00  01:50:41.5296  -32:36:15.102
G0749262  08:56:11  03:39:42.2206  -14:34:07.4136
G0771722  08:57:23  03:42:03.3526  -17:31:15.7764

GladeID   UT(Sep03)  RA_J2000   Dec_J2000
-----------------------------------------------
G0010892  08:25:01  23:14:54.2578  -20:59:45.3408
G0706844  08:26:12  23:17:27.2242  -10:01:50.466
G0713107  08:27:23  23:18:46.3769  -10:23:57.5232
G0703575  08:28:32  23:18:52.5439  -10:15:33.5268
G0551567  08:29:43  23:21:14.1725  -21:14:09.8736
G0553140  08:30:53  23:22:00.9228  -23:30:24.6924
G0582772  08:32:04  23:22:35.2735  -13:05:38.8392
G0001180  08:33:13  23:24:06.9506  -11:51:38.6856
G0800782  08:34:22  23:29:56.6969  -12:29:05.7048
G0606247  08:35:32  23:30:23.7377  -12:04:45.5448
G0820960  08:36:45  23:32:31.3476  -24:00:18.5652
G0556216  08:37:55  23:37:06.9288  -20:27:47.0988
G0612966  08:39:04  23:40:45.9667  -20:30:31.5108
G0666486  08:40:18  23:41:52.6685  -08:38:53.7144
G0579080  08:41:32  23:45:31.3037  -20:58:49.8036
G0584703  08:42:41  23:46:03.6036  -17:18:24.4296
G0682292  08:43:50  23:47:16.6992  -15:18:23.0148
G0751781  08:45:00  23:48:54.7118  -16:32:28.2588
G1852091  08:46:09  23:48:56.88    -16:32:24.684
G0748482  08:47:18  23:54:20.9254  -17:18:21.0348
G0733653  08:48:28  23:56:47.7247  -16:30:34.5924
G0755443  08:49:37  23:58:40.525   -17:33:31.7124
G0755095  09:30:03  00:07:10.2658  -21:47:11.5008
G0559232  09:31:16  00:11:12.5945  -33:34:42.8016
G0555127  09:32:27  00:13:02.9052  -24:12:52.5024
G0587522  09:33:37  00:19:04.9488  -22:56:11.184
G0665013  09:34:48  00:19:09.3768  -24:31:23.2068
G0552516  09:35:57  00:22:38.9513  -24:07:36.9624
G0823492  09:37:09  00:31:49.3798  -26:43:13.926
G0740509  09:38:18  00:36:27.3996  -27:47:07.4472
G0708432  09:39:27  00:53:54.0602  -31:05:43.8432
G1641290  09:40:41  01:04:30.36    -33:39:15.768
G0762311  09:41:50  01:06:12.2227  -30:10:41.1744
G1641121  09:43:01  01:19:41.448   -33:06:29.556
G0783834  09:44:11  01:19:47.6698  -33:04:59.9808
G0595298  09:45:23  01:23:14.8567  -32:50:28.6008
G0607401  09:46:32  01:24:34.5158  -33:10:24.6432
G0779486  09:47:42  01:24:50.3083  -31:45:23.8392
G0033739  09:48:57  01:47:44.4682  -33:36:05.5152
G0650576  09:50:11  02:15:38.0998  -33:00:31.5036
G0581927  09:51:23  02:17:13.6258  -33:00:41.5152
G1155066  09:52:36  02:35:13.4573  -29:36:16.6932
G0645820  09:53:46  02:38:45.1502  -30:48:23.3496
G0744351  09:54:55  02:44:15.8779  -31:56:31.3692
G0744589  09:56:06  02:46:41.6803  -25:20:47.8284
G0599710  09:57:18  02:56:13.0517  -28:02:31.5276
G0673848  09:58:27  02:56:42.421   -27:36:44.3808
G0607507  09:59:40  03:12:05.2524  -27:06:14.5728
G0605059  10:00:50  03:12:11.1941  -23:37:44.9004
G0803398  10:01:59  03:12:18.3096  -24:37:13.5336
G0767303  10:03:08  03:14:40.4534  -28:55:56.406
G0675048  10:04:20  03:16:22.8038  -23:48:36.7596
G0650576  10:34:49  02:15:38.0998  -33:00:31.5036
G0581927  10:35:56  02:17:13.6258  -33:00:41.5152
G0810505  10:37:10  02:25:46.3166  -26:06:50.7168
G1645381  10:38:19  02:28:16.464   -26:07:58.116
G0621255  10:39:28  02:35:21.6732  -25:31:39.7164
G0729094  10:40:37  02:37:35.3695  -26:22:04.1196
G0645820  10:41:47  02:38:45.1502  -30:48:23.3496
G0744351  10:42:56  02:44:15.8779  -31:56:31.3692
G0744589  10:44:05  02:46:41.6803  -25:20:47.8284
G0599710  10:45:17  02:56:13.0517  -28:02:31.5276
G0673848  10:46:26  02:56:42.421   -27:36:44.3808
G0625893  10:47:40  03:00:18.1229  -23:18:22.3344
G0805372  10:48:49  03:03:07.1767  -22:12:19.8108
G0691149  10:49:58  03:05:38.9611  -24:41:51.7488
G0607507  10:51:08  03:12:05.2524  -27:06:14.5728
G0605059  10:52:18  03:12:11.1941  -23:37:44.9004
G0803398  10:53:27  03:12:18.3096  -24:37:13.5336
G0642006  10:54:36  03:13:23.5886  -24:52:15.6216
G0675048  10:55:48  03:16:22.8038  -23:48:36.7596
G0699701  10:56:59  03:18:03.3581  -29:37:59.34
G0821941  10:58:08  03:20:51.7558  -30:47:19.1436
G0708674  10:59:18  03:23:17.8536  -27:39:21.1392
G0552792  11:00:29  03:25:27.6353  -22:29:25.9224
G0738507  11:01:38  03:25:44.6146  -26:23:17.1924
G0271141  11:02:52  03:27:20.8512  -13:44:54.3336
G0823848  11:04:03  03:28:43.7998  -19:57:07.7976
G0031069  11:05:14  03:29:55.7556  -28:46:03.9468
G0781950  11:06:26  03:30:46.6442  -20:31:26.634
G0707270  11:07:37  03:31:20.778   -26:06:09.2628
G0818993  11:08:46  03:31:24.3055  -20:10:06.4812
G0766666  11:25:41  02:26:36.2136  -23:25:01.3908
G1155066  11:26:52  02:35:13.4573  -29:36:16.6932
G0684350  11:28:02  02:37:33.9698  -27:26:30.12
G0634799  11:29:13  02:54:12.551   -33:43:07.7484
G0677246  11:30:24  03:03:53.8303  -24:33:54.4824
G0715403  11:31:33  03:08:11.7554  -22:55:22.3824
G0656204  11:32:43  03:11:09.8849  -25:19:14.4696
G0609459  11:33:52  03:11:34.5859  -26:53:47.4072
G0594595  11:35:01  03:12:26.5841  -27:08:24.594
G0675679  11:36:11  03:13:28.9006  -25:23:01.6548
G0723713  11:37:22  03:14:32.9746  -34:07:39.8316
G0767303  11:38:32  03:14:40.4534  -28:55:56.406
G0626814  11:39:41  03:16:08.7864  -29:18:20.412
G0625541  11:40:51  03:17:41.9623  -29:36:34.326
G0622813  11:42:05  03:18:03.7783  -19:29:15.0396
G0556222  11:43:16  03:19:17.3393  -27:07:40.5408
G0631899  11:44:26  03:20:03.3161  -27:00:56.2644
G0777203  11:45:35  03:22:07.9514  -27:34:54.5016
G0638952  11:46:49  03:24:05.4098  -16:18:36.864
G0675283  11:48:02  03:24:36.7548  -32:34:11.6292
G0626600  11:49:13  03:25:23.2042  -25:40:44.238
G0622938  11:50:25  03:26:14.7134  -21:01:52.3416
G0819935  11:51:36  03:27:41.0486  -28:23:19.8924
G0780661  11:52:47  03:28:47.6285  -23:23:25.5984
G0796339  11:53:59  03:29:21.1781  -28:08:00.0888
G0761570  11:55:08  03:30:14.8618  -24:21:31.9788
G0755903  11:56:18  03:30:17.7154  -24:21:08.9748
G0789550  11:57:29  03:32:49.2838  -32:40:07.4352
G0600093  11:58:42  03:33:48.695   -19:33:39.9996
G0563134  11:59:55  03:33:56.6153  -32:39:38.772
G0731177  12:22:07  03:31:31.3651  -27:28:47.0424
G0779774  12:23:18  03:32:31.4455  -22:23:43.6848
G0575234  12:24:28  03:34:42.1178  -20:50:50.2224
G0611152  12:25:38  03:37:31.627   -24:50:36.5928
G0627186  12:26:47  03:38:46.4126  -24:59:57.5088
G0277857  12:27:59  03:39:11.1814  -33:31:58.008
G0749262  12:29:14  03:39:42.2206  -14:34:07.4136
G0549570  12:30:23  03:42:03.0845  -18:29:00.9492
G0638801  12:31:33  03:42:17.6551  -22:44:51.9936
G0560055  12:32:43  03:43:20.5416  -18:28:37.974
G0664307  12:33:54  03:44:58.3282  -26:41:14.6832
G0712331  12:35:06  03:45:37.3142  -21:54:55.224
G0684551  12:36:15  03:47:07.5221  -24:31:50.304
G0705953  12:37:24  03:48:24.613   -21:25:53.2056
G0765196  12:38:34  03:49:00.8863  -22:14:25.908
G0629465  12:39:47  03:50:59.7655  -08:56:53.6352
G0772925  12:40:58  03:56:04.2718  -18:01:15.0636
G0771674  12:42:10  03:56:47.3474  -27:20:50.2512
G0665089  12:43:21  03:57:38.0897  -19:12:59.796
G0822929  12:44:30  03:57:46.9171  -26:13:29.8164
G0802406  12:45:40  03:58:51.2522  -27:47:49.6896
G0808004  12:46:49  03:59:06.2256  -27:20:33.9576
G0639673  12:47:58  03:59:20.5627  -24:19:26.022
G0734222  12:49:07  03:59:48.8268  -25:15:24.2388
G0729018  12:50:18  03:59:55.307   -24:57:49.2336
G0797844  12:51:27  03:59:55.8828  -24:29:20.238
G0605409  12:52:36  04:01:19.6171  -27:42:28.5732
G0822427  12:53:50  04:02:34.769   -22:18:22.4172
G0129198  12:55:03  04:08:07.4285  -08:49:45.3324
G0628998  12:56:18  04:09:06.1579  +15:30:50.0328
G0659256  13:03:23  03:38:40.5679  +09:58:11.9388

GCN Circular 25665

Subject
LIGO/Virgo S190901ap: NOT spectroscopy of AT2019pjv
Date
2019-09-05T10:25:51Z (6 years ago)
From
Erkki Kankare at University of Turku <erkki.kankare@utu.fi>
E. Kankare (U. Turku), P. Lundqvist (Stockholm U.), R. Kotak, S. Mattila (U. Turku), M. A. P. Torres (IAC/ULL/SRON), T. Heikkil�, H. Kuncarayakti, T. Reynolds (U. Turku), S. Moran (NOT), D. Steeghs, J. Lyman (U. Warwick), T. Pursimo, J. Martikainen (NOT), report on behalf of a larger GOTO and NOT collaboration:

We obtained a spectrum of AT2019pjv discovered by MASTER (Lipunov et al., GCN #25649) that was also observed by GOTO (Ackley et al., GCN #25654) and HMT (Yu et al., GCN #25659) within the sky localization region of the LIGO/Virgo event S190901ap (LVC et al., GCN #25606, GCN #25614). 

The 1200 sec observation was obtained at the 2.56 m Nordic Optical Telescope equipped with ALFOSC, and started at 2019-09-04T20:42:48 (range 350-960 nm; resolution 1.6 nm). Reasonable matches are obtained using SNID (Blondin & Tonry, 2007, ApJ, 666, 1024) and template set 2.0 with SN 1991T-like type Ia SNe 2005eq, 1998es, 1999aa roughly 8 days before maximum at z = 0.013 +/- 0.007. Our classification confirms that previously reported by Nascimbeni et al. (GCN #25661). However, our redshift estimate is somewhat lower than that reported by Nascimbeni et al., but as we do not detect any narrow lines that could be from a putative host galaxy, we cannot fully exclude the possibility that AT2019pjv is not directly associated with MCG +05-41-001 at z = 0.023 (SDSS, DR12). This obviously has no effect on the main conclusion of Nascimbeni et al. that AT2019pjv is unrelated to S190901ap.

Based on observations taken with the Nordic Optical Telescope, operated by the Nordic Optical Telescope Scientific Association at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofisica de Canarias. The data presented here were obtained with ALFOSC, which is provided by the Instituto de Astrofisica de Andalucia (IAA) under a joint agreement with the University of Copenhagen and NOTSA.

GCN Circular 25666

Subject
LIGO/Virgo S190901ap : No significant candidates in TAROT-GRANDMA
Date
2019-09-05T11:42:43Z (6 years ago)
From
Kateryna Barynova at Kiev Uni., GRANDMA <katiaffoni@gmail.com>
K. Barynova (CEA-Irfu/Univ Kiev), W. Lin (THU), D. Corre (LAL),
S. Antier (APC),  M. Boer (Artemis), N. Christensen (Artemis),
L. Eymar (Artemis), A. Klotz (IRAP), K. Noysen (Artemis, IRAP),
S. Basa (LAM), J.G. Ducoin (LAL), M. Coughlin (Caltech),
D. Coward (OzGrav-UWA), P. Hello (LAL), N. Leroy (LAL),
D. Turpin (NAOC), C. Thone (HETH/IAA-CSIC), X. Wang (THU)

Report on behalf of the TAROT network and GRANDMA collaborations.

We performed tiled observations of the LIGO/Virgo event S190901ap
event (GCN #25606) with the TAROT-Chile (TCH), TAROT-Calern (TCA)
and TAROT-Reunion (TRE) telescopes operating in the visible
located respectively at La Silla ESO observatory (LaS/ESO),
the Calern site at the Cote d'Azur observatory and at
La Reunion Island, France.

The observation started for TRE at 09/01/19 23:57:14 UTC which
corresponds approximately to 27 minutes after the GW trigger time,
for TCA at 09/02/19 00:45:34 UTC which corresponds approximately
to 75 minutes after the GW trigger time, and for TCH at 09/02/19
03:59:57 UTC which corresponds approximately to 269 minutes
after the GW trigger time.

We performed the following tiled observations :


+-------+------------+------------+---------+---------+---------+
| Tele  | TStart     | TEnd       | RA      | DEC     |   Proba |
| scope | [UTC]      | [UTC]      | [deg]   | [deg]   |     [%] |
|-------+------------+------------+---------+---------+---------|
|  TRE  | 2019-09-01 | 2019-09-02 | 56.1    | -22.445 |     0.5 |
|       | 23:57:14   | 19:55:53   |         |         |         |
|  TRE  | 2019-09-02 | 2019-09-02 | 63.563  | -18.355 |     0.5 |
|       | 00:10:23   | 21:08:16   |         |         |         |
|  TRE  | 2019-09-02 | 2019-09-02 | 59.173  | -18.355 |     0.5 |
|       | 21:40:00   | 21:46:28   |         |         |         |
|  TRE  | 2019-09-02 | 2019-09-04 | 48.853  | -26.536 |     0.5 |
|       | 21:52:55   | 01:39:05   |         |         |         |
|  TRE  | 2019-09-02 | 2019-09-03 | 60.705  | -10.173 |     0.5 |
|       | 22:11:52   | 21:42:47   |         |         |         |
|  TRE  | 2019-09-02 | 2019-09-03 | 62.1    | -14.264 |     0.4 |
|       | 22:24:38   | 00:38:54   |         |         |         |
|  TRE  | 2019-09-02 | 2019-09-04 | 67.954  | -18.355 |     0.5 |
|       | 22:56:19   | 00:35:23   |         |         |         |
|  TRE  | 2019-09-02 | 2019-09-02 | 57.814  | -14.264 |     0.5 |
|       | 23:21:47   | 23:28:20   |         |         |         |
|  TRE  | 2019-09-02 | 2019-09-03 | 65.1    | -22.445 |     0.5 |
|       | 23:35:00   | 20:58:07   |         |         |         |
|  TRE  | 2019-09-03 | 2019-09-03 | 50.749  | -30.627 |     0.4 |
|       | 00:51:12   | 22:14:50   |         |         |         |
|  TRE  | 2019-09-03 | 2019-09-03 | 44.178  | -26.536 |     0.4 |
|       | 19:21:53   | 19:28:21   |         |         |         |
|  TRE  | 2019-09-03 | 2019-09-03 | 55.614  | -30.627 |     0.4 |
|       | 21:55:02   | 22:01:30   |         |         |         |
|  TRE  | 2019-09-03 | 2019-09-03 | 70.671  | -14.264 |     0.5 |
|       | 22:39:59   | 22:46:27   |         |         |         |
|  TRE  | 2019-09-03 | 2019-09-03 | 51.6    | -22.445 |     0.5 |
|       | 22:53:01   | 22:59:35   |         |         |         |
|  TRE  | 2019-09-03 | 2019-09-03 | 66.386  | -14.264 |     0.5 |
|       | 23:05:36   | 23:12:04   |         |         |         |
|  TRE  | 2019-09-03 | 2019-09-03 | 60.6    | -22.445 |     0.5 |
|       | 23:18:31   | 23:24:59   |         |         |         |
|-------+------------+------------+---------+---------+---------|
|  TCA  | 2019-09-02 | 2019-09-04 | 59.998  | -12.967 |     0.1 |
|       | 00:45:34   | 01:00:07   |         |         |         |
|  TCA  | 2019-09-02 | 2019-09-04 | 61.264  | -11.112 |     0.1 |
|       | 00:52:23   | 01:51:39   |         |         |         |
|  TCA  | 2019-09-02 | 2019-09-02 | 57.214  | -18.535 |     0.1 |
|       | 00:59:12   | 01:05:42   |         |         |         |
|  TCA  | 2019-09-02 | 2019-09-02 | 66.919  | -11.112 |     0.1 |
|       | 01:11:30   | 03:28:20   |         |         |         |
|  TCA  | 2019-09-02 | 2019-09-04 | 60.629  | -14.823 |     0.1 |
|       | 01:18:19   | 02:39:22   |         |         |         |
|  TCA  | 2019-09-02 | 2019-09-03 | 63.75   | -9.256  |     0.1 |
|       | 01:25:08   | 02:45:10   |         |         |         |
|  TCA  | 2019-09-02 | 2019-09-03 | 58.093  | -12.967 |     0.1 |
|       | 01:37:24   | 03:36:21   |         |         |         |
|  TCA  | 2019-09-02 | 2019-09-02 | 69.375  | -9.256  |     0.1 |
|       | 01:44:14   | 04:00:59   |         |         |         |
|  TCA  | 2019-09-02 | 2019-09-04 | 60.95   | -9.256  |     0.1 |
|       | 01:53:18   | 01:39:22   |         |         |         |
|  TCA  | 2019-09-02 | 2019-09-04 | 52.663  | -20.39  |     0.1 |
|       | 02:16:56   | 02:05:19   |         |         |         |
|  TCA  | 2019-09-02 | 2019-09-02 | 61.902  | -12.967 |     0.1 |
|       | 02:23:45   | 02:30:15   |         |         |         |
|  TCA  | 2019-09-02 | 2019-09-02 | 64.084  | -11.112 |     0.1 |
|       | 02:35:44   | 02:42:14   |         |         |         |
|  TCA  | 2019-09-02 | 2019-09-02 | 59.646  | -18.535 |     0.1 |
|       | 02:42:33   | 02:49:03   |         |         |         |
|  TCA  | 2019-09-02 | 2019-09-02 | 61.602  | -18.535 |     0.1 |
|       | 02:49:22   | 02:55:53   |         |         |         |
|  TCA  | 2019-09-02 | 2019-09-02 | 72.2    | -9.256  |     0.1 |
|       | 03:15:01   | 03:17:01   |         |         |         |
|  TCA  | 2019-09-02 | 2019-09-02 | 66.575  | -9.256  |     0.1 |
|       | 03:40:50   | 03:47:21   |         |         |         |
|  TCA  | 2019-09-03 | 2019-09-03 | 55.713  | -12.967 |     0.1 |
|       | 00:21:30   | 02:38:21   |         |         |         |
|  TCA  | 2019-09-03 | 2019-09-03 | 63.807  | -12.967 |     0.1 |
|       | 00:54:03   | 01:00:33   |         |         |         |
|  TCA  | 2019-09-03 | 2019-09-04 | 50.674  | -20.39  |     0.1 |
|       | 01:00:52   | 00:53:16   |         |         |         |
|  TCA  | 2019-09-03 | 2019-09-03 | 69.521  | -12.967 |     0.1 |
|       | 01:26:26   | 03:43:11   |         |         |         |
|  TCA  | 2019-09-03 | 2019-09-04 | 57.079  | -16.679 |     0.1 |
|       | 01:33:16   | 01:25:40   |         |         |         |
|  TCA  | 2019-09-03 | 2019-09-04 | 54.652  | -20.39  |     0.1 |
|       | 01:40:05   | 01:32:31   |         |         |         |
|  TCA  | 2019-09-03 | 2019-09-03 | 67.617  | -12.967 |     0.1 |
|       | 01:52:16   | 04:08:27   |         |         |         |
|  TCA  | 2019-09-03 | 2019-09-04 | 56.779  | -14.823 |     0.1 |
|       | 02:05:54   | 01:58:29   |         |         |         |
|  TCA  | 2019-09-03 | 2019-09-03 | 55.789  | -18.535 |     0.1 |
|       | 02:18:13   | 02:24:43   |         |         |         |
|  TCA  | 2019-09-03 | 2019-09-03 | 57.495  | -11.112 |     0.1 |
|       | 02:25:02   | 02:31:32   |         |         |         |
|  TCA  | 2019-09-03 | 2019-09-03 | 70.213  | -11.112 |     0.1 |
|       | 03:23:02   | 03:29:32   |         |         |         |
|  TCA  | 2019-09-04 | 2019-09-04 | 53.208  | -16.679 |     0.1 |
|       | 02:30:32   | 02:37:03   |         |         |         |
|-------+------------+------------+---------+---------+---------|
|  TCH  | 2019-09-02 | 2019-09-04 | 57.079  | -19.959 |     0.1 |
|       | 03:59:57   | 07:02:59   |         |         |         |
|  TCH  | 2019-09-02 | 2019-09-02 | 55.363  | -25.414 |     0.1 |
|       | 04:06:45   | 08:46:05   |         |         |         |
|  TCH  | 2019-09-02 | 2019-09-02 | 61.285  | -25.414 |     0.1 |
|       | 04:13:33   | 04:20:03   |         |         |         |
|  TCH  | 2019-09-02 | 2019-09-02 | 51.238  | -25.495 |     0.1 |
|       | 04:20:21   | 06:35:40   |         |         |         |
|  TCH  | 2019-09-02 | 2019-09-04 | 68.686  | -16.323 |     0.1 |
|       | 04:51:50   | 09:38:48   |         |         |         |
|  TCH  | 2019-09-02 | 2019-09-02 | 43.554  | -30.868 |     0.1 |
|       | 04:58:39   | 09:58:11   |         |         |         |
|  TCH  | 2019-09-02 | 2019-09-02 | 54.652  | -23.595 |     0.1 |
|       | 05:05:27   | 07:34:48   |         |         |         |
|  TCH  | 2019-09-02 | 2019-09-02 | 62.35   | -14.505 |     0.1 |
|       | 05:24:17   | 05:30:47   |         |         |         |
|  TCH  | 2019-09-02 | 2019-09-02 | 59.998  | -18.141 |     0.1 |
|       | 05:31:05   | 08:00:06   |         |         |         |
|  TCH  | 2019-09-02 | 2019-09-02 | 57.214  | -21.777 |     0.1 |
|       | 05:37:53   | 05:44:23   |         |         |         |
|  TCH  | 2019-09-02 | 2019-09-02 | 60.95   | -19.959 |     0.1 |
|       | 05:56:40   | 06:03:10   |         |         |         |
|  TCH  | 2019-09-02 | 2019-09-02 | 58.093  | -18.141 |     0.1 |
|       | 06:03:28   | 06:09:58   |         |         |         |
|  TCH  | 2019-09-02 | 2019-09-02 | 53.352  | -25.414 |     0.1 |
|       | 06:35:58   | 06:42:28   |         |         |         |
|  TCH  | 2019-09-02 | 2019-09-02 | 56.641  | -23.595 |     0.1 |
|       | 06:42:46   | 06:49:16   |         |         |         |
|  TCH  | 2019-09-02 | 2019-09-02 | 59.014  | -19.959 |     0.1 |
|       | 09:38:11   | 09:44:41   |         |         |         |
|  TCH  | 2019-09-02 | 2019-09-02 | 45.684  | -30.868 |     0.1 |
|       | 10:10:53   | 10:15:08   |         |         |         |
|  TCH  | 2019-09-03 | 2019-09-04 | 65.572  | -21.777 |     0.1 |
|       | 04:34:32   | 08:46:48   |         |         |         |
|  TCH  | 2019-09-03 | 2019-09-03 | 55.691  | -23.595 |     0.1 |
|       | 05:06:45   | 09:32:17   |         |         |         |
|  TCH  | 2019-09-03 | 2019-09-04 | 53.742  | -32.686 |     0.1 |
|       | 05:13:33   | 09:25:11   |         |         |         |
|  TCH  | 2019-09-03 | 2019-09-03 | 55.422  | -16.323 |     0.1 |
|       | 05:32:44   | 07:49:08   |         |         |         |
|  TCH  | 2019-09-03 | 2019-09-04 | 57.787  | -16.323 |     0.1 |
|       | 05:39:32   | 07:41:53   |         |         |         |
|  TCH  | 2019-09-03 | 2019-09-04 | 67.617  | -18.141 |     0.1 |
|       | 05:51:49   | 10:04:18   |         |         |         |
|  TCH  | 2019-09-03 | 2019-09-04 | 57.2    | -14.505 |     0.1 |
|       | 05:58:37   | 10:11:06   |         |         |         |
|  TCH  | 2019-09-03 | 2019-09-03 | 60.632  | -16.323 |     0.1 |
|       | 06:05:25   | 08:20:57   |         |         |         |
|  TCH  | 2019-09-03 | 2019-09-04 | 64.821  | -19.959 |     0.1 |
|       | 06:24:24   | 06:17:37   |         |         |         |
|  TCH  | 2019-09-03 | 2019-09-04 | 52.826  | -21.777 |     0.1 |
|       | 06:31:13   | 08:33:12   |         |         |         |
|  TCH  | 2019-09-03 | 2019-09-04 | 55.144  | -20.909 |     0.1 |
|       | 06:38:01   | 08:40:00   |         |         |         |
|  TCH  | 2019-09-03 | 2019-09-04 | 53.208  | -19.959 |     0.1 |
|       | 06:56:39   | 04:39:47   |         |         |         |
|  TCH  | 2019-09-03 | 2019-09-04 | 52.108  | -17.273 |     0.1 |
|       | 07:03:27   | 06:56:11   |         |         |         |
|  TCH  | 2019-09-03 | 2019-09-04 | 51.238  | -25.495 |     0.1 |
|       | 07:29:02   | 09:31:59   |         |         |         |
|  TCH  | 2019-09-03 | 2019-09-04 | 54.283  | -18.141 |     0.1 |
|       | 08:27:57   | 08:21:00   |         |         |         |
|  TCH  | 2019-09-03 | 2019-09-03 | 56.188  | -18.141 |     0.1 |
|       | 09:00:05   | 09:06:35   |         |         |         |
|  TCH  | 2019-09-03 | 2019-09-04 | 68.45   | -14.505 |     0.1 |
|       | 10:05:03   | 09:57:30   |         |         |         |
|  TCH  | 2019-09-04 | 2019-09-04 | 62.608  | -23.595 |     0.1 |
|       | 05:57:31   | 06:04:01   |         |         |         |
+-------+------------+------------+---------+---------+---------+

TStart and TEnd refer respectively to the time of the first and last
exposure for a given tile. Observations are not necessarily continuous
in this interval. The "Probability" column refers to the 2D spatial
probability of the GW skymap enclosed in a given tile. Each tile is
1.9x1.9 degrees for both TCA and TCH and 4.2x4.2 degrees for TRE.

The coordinating observations cover about 9% of the cumulative
probability of the LALInference skymap available on Sep 2, 2019
11:21:57 UTC. The typical limiting magnitude in AB mode is 18.0
for a 60.0 s exposure for TCH and TCA and 17.0 for
a 60.0 s exposure for TRE.

The coverage map is available at:
https://grandma-owncloud.lal.in2p3.fr/index.php/s/GDhyzNjw9xGJALH


No significant transient candidates were found during our
low latency 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.

GCN Circular 25674

Subject
LIGO/Virgo S190901ap: Second Epoch Hobby-Eberly Telescope observations of ZTF19abvionh
Date
2019-09-06T02:32:45Z (6 years ago)
From
J. Craig Wheeler at U.Texas Austin <wheel@astro.as.utexas.edu>
M. J. B. Rosell, Greg Zeimann, Karl Gebhardt, Aaron Zimmerman, Matthew Shetrone, Chris Fryer, J. Craig Wheeler, Steve Odewahn, and Nathan McReynolds on behalf of the LIGO Hobby-Eberly Telescope Response (LIGHETR) team,report a second epoch of spectroscopic observations of the optical transient ZTF19abvionh(Kool et al. GCN #25616, Rosell et al. GCN #25620, Kumar et al. GCN 25632, Burdge et al. GCN #25638) on 9/03/19. Observations were made with the VIRUS IFU spectrograph that covers the wavelength range of 3500 to 5500 Angstroms and with the blue and orange arms of the LRS2 spectrograph that cover the range 3400 to 7000 Angstroms. We confirm the emission lines at 4124 Angstroms and 5370 Angstroms that correspond to [O II] 3727 and Hbeta at a redshift of ~0.1 associated with S0 galaxy GALEXASC J165500.03+140301.3. We detect very little change in the amplitude or spectrum compared with the first epoch of observations. The flux at 5700 Angstroms is roughly consistent with the photometry reported by Kumar et al. The optical candidate shows a blue continuum corresponding to a BB temperature of about 10,500K. The VIRUS and LRS2 spectra are consistent in the overlap region. Both sets of data show a somewhat broadened (~25 Angstroms FWHM) emission feature at ~4686 Angstroms. The LRS2 data also show a somewhat smaller emission feature at ~6563 Angstroms with roughly the same width. We tentatively identify the former as He II perhaps blended with N III and the latter with Halpha, both with negligible redshift. The line broadening suggests a velocity of ~1700 km/s. The optical candidate does not have the properties expected of a merger event and hence is unrelated to S190901ap.

GCN Circular 25675

Subject
LIGO/Virgo S190901ap: ZTF19abwvals is a type-Ia SN near maximum
Date
2019-09-06T12:41:49Z (6 years ago)
From
Daniele B Malesani at DTU Space <malesani@space.dtu.dk>
L. Izzo (DARK/NBI), G. Leloudas (DTU Space), S. H. Bruun (DARK/NBI), K. 
E. Heintz (Univ. Iceland), B. Milvang-Jensen (DAWN/NBI), J. Hjorth 
(DARK/NBI), J. P. U. Fynbo (DAWN/NBI), D. B. Malesani (DTU Space), S. 
Piranomonte (INAF/OARm), T. Pursimo (NOT), J. Martikainen (NOT and Univ. 
Helsinki), report on behalf of a larger collaboration:

We observed the transient ZTF19abwvals (Stein et al., GCN 25656) 
discovered by the Zwicky Transient Facility as a candidate counterpart 
of the LIGO/Virgo GW event S190901ap (LIGO Scientific Collaboration and 
Virgo Collaboration, GCNs 25606, 25614), using the Nordic Optical 
Telescope equipped with the ALFOSC spectrograph. A spectrum by 2x1200 s 
was acquired covering the wavelength range 3200-9600 AA, starting on 
2019 September 5.20 UT.

In the acquisition image (taken without filter) the transient is 
detected, approximately 0.9" to the NW of the galaxy nucleus and hence 
blended with it given the seeing of approximately 1". In the spectral 
extraction, a sizable contribution from the host galaxy is present.

Template-matching using SNID (Blondin & Tonry, 2007, ApJ, 666, 1024) and 
DASH (https://astrodash.readthedocs.io) shows that ZTF19abwvals is a 
normal type-Ia SN at a phase of 4-6 days after maximum, at a redshift z 
= 0.091 +- 0.004. The redshift is consistent with the SDSS photometric 
value z_ph = 0.13 +- 0.03 of the host galaxy. Considering the foreground 
Galactic extinction (A_r = 1.04 mag) and the measurement by Stein et al. 
(GCN 25656), the absolute magnitude of the transient at z = 0.091 is M_r 
~ -19.4, consistent with a type-Ia SN near peak.

The above classification excludes ZTF19abwvals as a counterpart of 
S190901ap.

GCN Circular 25688

Subject
LIGO/Virgo S190901ap : No significant candidates found in GRANDMA citizen science observations
Date
2019-09-09T13:53:09Z (6 years ago)
From
Jean-Gregoire Ducoin at LAL <ducoin@lal.in2p3.fr>
J.G. Ducoin (LAL), S. Antier (APC), B. Chabert (IRAP), D. Corre (LAL), 
A. Klotz (IRAP), D. Turpin (NAOC), S. Basa (LAM), M. Boer (Artemis),
N. Christensen (Artemis), A. Coleiro (APC), M. Coughlin (Caltech), 
D. Coward (OzGrav-UWA), P. Hello (LAL), N. Leroy (LAL), 
C. Thone (HETH/IAA-CSIC), X. Wang (THU)

Report on behalf of the GRANDMA collaboration.

We performed galaxy-targeted observations of the LIGO/Virgo event 
S190901ap event (GCN #25606) with the amator astronomers 
of GRANDMA citizen science program "kilonova-catcher" created 
by CNRS/IRAP and CNRS/LAL.

Denis St-Gelais, Raymond Kneip and Peter Jaquiery performed 
galaxy-targeted observations in clear filter of the S190901ap event. 
Denis St-Gelais imaged 8 fields with a 36-cm telescope located 
in Quer��taro (Mexico): the typical limiting magnitude is 19 for 
a 60.0 s exposure. Peter Jaquiery imaged 8 fields
with a 35-cm telescope at Berverly-Begg Observatory (New Zealand):
the typical magnitude is 18.5 for an exposure time of 10 min. 
Raymond Kneip imaged four fields with K26 35-cm telescope
at Contern observatory (Luxembourg): the typical limiting magnitude 
is 18.5 mag for 20 min exposure.

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 with the distance of the 
GW event.

No significant transient candidates were found during our analysis.

The coverage map is available at:
https://grandma-owncloud.lal.in2p3.fr/index.php/s/GDhyzNjw9xGJALH


The list of the galaxies we observed is given 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.


+----------+----------+-----------------------+--------+--------+------+
|TStart    | TEnd     | Galaxy                | RA     | DEC    | Dist.|
|[UTC]     | [UTC]    | name                  | [deg]  | [deg]  | [Mpc]|
|----------+----------+-----------------------+--------+--------+------|
|2019-09-02|2019-09-02|HyperLEDA 58263        |247.161 |39.0833 |142.86|
| 20:45:30 | 20:57:30 |                       |        |        |      |
|2019-09-03|2019-09-03|2MASS 03582008-0532062 |59.5837 |-5.5351 |280.33|
| 04:10:12 | 04:36:04 |                       |        |        |      |
|2019-09-03|2019-09-03|2MASS 17054435+2214502 |256.4348|22.2473 |213.86|
| 04:42:08 | 05:09:20 |                       |        |        |      |
|2019-09-03|2019-09-03|HyperLEDA HIZOAJ1825-07|276.488 |-7.1932 |162.92|
| 05:21:17 | 05:50:26 |                       |        |        |      |
|2019-09-03|2019-09-03|HyperLEDA HIZOAJ1814-08|273.762 |-8.6037 |160.01|
| 05:55:27 | 06:04:02 |                       |        |        |      |
|2019-09-03|2019-09-03|2MASS 02262568-2820588 |36.6070 |-28.3497|311.49|
| 07:23:29 | 07:50:49 |                       |        |        |      |
|2019-09-03|2019-09-03|2MASS 02351345-2936166 |38.80607|-29.6046|267.85|
| 08:06:32 | 08:42:21 |                       |        |        |      |
|2019-09-03|2019-09-03|2MASS 03111883-2046184 |47.82849|-20.7718|305.52|
| 09:03:31 | 09:30:46 |                       |        |        |      |
|2019-09-03|2019-09-03|2MASS 03415732-1106138 |55.48884|-11.1039|246.10|
| 09:36:01 | 10:34:18 |                       |        |        |      |
|2019-09-03|2019-09-03|2MASS 23263752-6106015 |351.6563|-61.1004|177.63|
| 09:44:34 | 10:04:34 |                       |        |        |      |
|2019-09-03|2019-09-03|HyperLEDA HIZOAJ1825-07|276.488 |-7.19323|162.92|
| 10:21:07 | 10:41:07 |                       |        |        |      |
|2019-09-03|2019-09-03|HyperLEDA HIZOAJ1814-08|273.762 |-8.60367|160.01|
| 11:15:29 | 11:35:29 |                       |        |        |      |
|2019-09-03|2019-09-03|HyperLEDA ESO410-024   |9.11416 |-27.7854|149.38|
| 11:28:45 | 11:37:45 |                       |        |        |      |
|2019-09-03|2019-09-03|HyperLEDA ESO351-016   |13.09514|-35.0007|200.54|
| 12:21:09 | 12:31:09 |                       |        |        |      |
|2019-09-03|2019-09-03|HyperLEDA ESO411-028   |13.47525|-31.0955|137.69|
| 12:38:20 | 12:48:20 |                       |        |        |      |
|2019-09-03|2019-09-03|HyperLEDA ESO352-002   |16.1265 |-33.6544|141.76|
| 12:58:27 | 13:18:27 |                       |        |        |      |
|2019-09-03|2019-09-03|2MASS 01234572-5848208 |20.94051|-58.8058|205.94|
| 13:28:49 | 13:48:49 |                       |        |        |      | 
|2019-09-03|2019-09-03|2MASS 16350144+3054117 |248.7560|30.90327|300.65|
| 19:52:00 | 20:15:00 |                       |        |        |      |
|2019-09-03|2019-09-03|2MASS 17111820+1650431 |257.8259|16.84531|252.86|
| 20:19:00 | 20:42:00 |                       |        |        |      |
|2019-09-03|2019-09-03|2MASS 18350342+3241471 |278.7642|32.69643|258.88|
| 20:45:00 | 21:08:00 |                       |        |        |      |
+----------+----------+-----------------------+--------+--------+------+


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 
GRANDMA web pages and the citizen science program "kilonova-catcher"  
are available on https://grandma-kilonovacatcher.lal.in2p3.fr/

GCN Circular 25689

Subject
LIGO/Virgo S190901ap: Gaia Photometric Alerts transient candidates
Date
2019-09-09T14:35:53Z (6 years ago)
From
Zuzanna Kostrzewa-Rutkowska at SRON <z.p.kostrzewa@sron.nl>
Z. Kostrzewa-Rutkowska (Leiden Observatory), 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 S190901ap (the LIGO Scientific Collaboration and the Virgo Collaboration, GCN 25606):

---------------------------------------------------------------------------
Name      TNSid Date [TCB]          RaDeg DecDeg AlertMag URL
---------------------------------------------------------------------------
SN candidates:
Gaia19dyu AT2019psg 2019-09-05T07:22:03 40.96499 -58.29228 18.95 http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19dyu/
Gaia19dxp AT2019pqc 2019-09-06T07:19:43 43.59650 -53.69043 18.88 http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19dxp/
Gaia19dxf AT2019pns 2019-09-04T19:11:27 57.21955 -55.42570 17.87 http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19dxf/
Gaia19dxd AT2019pnr 2019-09-05T13:24:10 37.51050 -58.24664 18.99 http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19dxd/
Gaia19dxc AT2019pnq 2019-09-05T12:31:35 86.95212 -25.16602 18.57 http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19dxc/
---------------------------------------------------------------------------
posible CV candidates:
Gaia19dyy AT2019psj 2019-09-06T22:48:33 282.48546 -7.85814 18.00 http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19dyy/
Gaia19dym AT2019pra 2019-09-06T15:16:29 274.56785 6.03930 18.13 http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19dym/
Gaia19dxx AT2019pqq 2019-09-05T23:03:26 275.72895 7.81160 17.53 http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19dxx/
Gaia19dxt AT2019pqe 2019-09-04T21:14:57 279.59279 8.11615 18.85 http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19dxt/
---------------------------------------------------------------------------
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. DE and PGJ acknowledge support from the European Research Council under ERC Consolidator Grant agreement no 647208.

GCN Circular 25716

Subject
LIGO/Virgo S190901ap: Gaia Photometric Alerts transient candidates
Date
2019-09-10T13:38:57Z (6 years ago)
From
Zuzanna Kostrzewa-Rutkowska at SRON <z.p.kostrzewa@sron.nl>
Z. Kostrzewa-Rutkowska (Leiden Observatory), 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 S190901ap (the LIGO Scientific Collaboration and the Virgo Collaboration, GCN 25606):

---------------------------------------------------------------------------
Name      TNSid Date [TCB]          RaDeg DecDeg AlertMag URL
---------------------------------------------------------------------------
Gaia19dzv AT2019pwe 2019-09-08T13:35:59 20.00637 -51.06273 18.85 http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19dzv/
Gaia19dzi AT2019piw 2019-09-07T18:33:54 79.57534 -19.22286 18.17 http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19dzi/


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. DE and PGJ acknowledge support from the European Research Council under ERC Consolidator Grant agreement no 647208.

GCN Circular 25724

Subject
LIGO/Virgo S190901ap: WHT spectroscopy of Gaia19dzi
Date
2019-09-11T06:10:54Z (6 years ago)
From
Giacomo Cannizzaro at SRON <g.cannizzaro@sron.nl>
G. Cannizzaro (SRON/Radboud Univ), I. Pastor-Marazuela (API/ASTRON), P. Jonker (SRON/Radboud Univ) report on behalf of the GW@WHT collaboration:

We obtained optical spectroscopy of Gaia19dzi (GCN 25716), an optical transient within the LIGO/Virgo S190901ap  sky localisation (GCN 25606) with the ACAM instrument mounted on the William Herschel Telescope located at the Roque de Los Muchachos Observatory, La Palma, Spain. We cross-correlate the transient spectra with a library of supernova template spectra using the code SNID (Blondin and Tonry, 2007). 


Gaia19dzi is classified as a SNIa, with a redshift of z=0.06. 

[GCN OPS NOTE(11sep19):  Per author's request, in the Subject-line and
first sentence the "S190910ap" was changed to "S190901ap".]

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