LIGO/Virgo S190727h

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
S190727h
 in a time range of 1000 seconds [3] centered on the alert event time
(2019-07-27 05:55:13.986 UTC to 2019-07-27 06:11:53.986 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 S190727h 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 S190727h ranges from  0.035 to 0.983 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
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  (2018) and Countryman et
al.arXiv:1901.05486
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  (2019)
[2] Braun et al., Astroparticle Physics 29, 299 (2008)
[3] Baret et al., Astroparticle Physics 35, 1 (2011)

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 S190727h errorbox  179 sec after notice time and 738 sec after trigger time at 2019-07-27 06:15:51 UT, with upper limit up to  17.3 mag. The observations began at zenit distance = 82 deg. The sun  altitude  is -65.7 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=10581

We obtain a following upper limits.  

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

     814 | 2019-07-27 06:15:51 |         MASTER-OAFA | (  9h 24m 51.16s , -66d 49m 03.06s) |   C |   150 | 17.3 |        
Filter C is a clear (unfiltred) band. 


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

The LIGO Scientific Collaboration and the Virgo Collaboration report:


We identified the compact binary merger candidate S190727h during
real-time processing of data from LIGO Hanford Observatory (H1), LIGO
Livingston Observatory (L1), and Virgo Observatory (V1) at 2019-07-27
06:03:33.986 UTC (GPS time: 1248242631.986). The candidate was found
by the GstLAL [1], CWB [2], PyCBC Live [3], MBTAOnline [4], and SPIIR
[5] analysis pipelines.

S190727h is an event of interest because its false alarm rate, as
estimated by the online analysis, is 1.4e-10 Hz, or about one in 1e2
years. The event's properties can be found at this URL:

https://gracedb.ligo.org/superevents/S190727h

The classification of the GW signal, in order of descending
probability, is BBH (92%), Terrestrial (5%), MassGap (3%), NSBH (<1%),
or BNS (<1%).

Assuming the candidate is astrophysical in origin, there is strong
evidence against the lighter compact object having a mass < 3 solar
masses (HasNS: <1%). Using the masses and spins inferred from the
signal, there is strong evidence against matter outside the final
compact object (HasRemnant: <1%).

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
[6], distributed via GCN notice about 8 minutes after the candidate

For the bayestar.fits.gz sky map, the 90% credible region is 841
deg2. Marginalized over the whole sky, the a posteriori luminosity
distance estimate is 2022 +/- 516 Mpc (a posteriori mean +/- standard
deviation).

Note that the preliminary GCN notice incorrectly reported
the classification as 99% Terrestrial, and the incorrect skymap was
associated with the event. These have now been corrected.

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] Klimenko et al. PRD 93, 042004 (2016)
 [3] Nitz et al. PRD 98, 024050 (2018)
 [4] Adams et al. CQG 33, 175012 (2016)
 [5] Qi Chu, PhD Thesis, The University of Western Australia (2017)
 [6] Singer & Price PRD 93, 024013 (2016)

S. Sugita, M. Serino (AGU),
N. Kawai, M. Sugizaki (Tokyo Tech), H. Negoro (Nihon U.),
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 S190727h at 2019-07-27 06:03:33.985 UTC (GCN 25164
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 ).

At the trigger time of S190727h, the high-voltage of MAXI/GSC was on.
The instantaneous field of view of GSC at the GW trigger time covered
2% of the 90% credible region
of the bayestar sky map, in which we found no significant new X-ray source.
The first one-orbit (92 min) scan observation with GSC after the event
covered 30%
of the 90% credible region of the bayestar skymap from 06:03:33 to
07:35:31 UTC (T0+0 to T0+5518 sec).

No significant new source was found in the region in the one-orbit
scan 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.

Maeve Doyle (UCD, Ireland), Alexander Lutovinov (IKI, Moscow)
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 S190727h (GCN 25164
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 ).

At the time of the event (2019-07-27 06:03:33 UTC, hereafter T0),
INTEGRAL was operating in nominal mode. The peak of the event
localization probability was at an angle of 127 deg with respect to
the spacecraft pointing axis. This orientation implies strongly
suppressed (3.6% of optimal) response of ISGRI, somewhat suppressed
(44% of optimal) response of IBIS/Veto, and somewhat suppressed 
(52% of optimal) response of SPI-ACS.

The background within +/-300 seconds around the event was very stable
(excess variance 1.1).

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 2.1e-07 erg/cm^2 (within the
50% probability containement 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 ~1.8e-07 (5.9e-08)
erg/cm^2/s at 1 s (8 s) time scale in 75-2000 keV energy range.

For the mean reported distance 2022.0 Mpc this corresponds to the
limit on the total isotropic equivalent energy in 1 s of 1.1e+50 erg 
for the short GRB spectrum and for a long GRB spectrum isotropic
equivalent luminosity in 1 s (8 s) of 8.7e+49 erg/s (2.9e+49 erg/s)

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

A. Ursi (INAF/IAPS), M. Pilia (INAF/OA-Cagliari), M. Tavani (INAF/IAPS, and
Univ. Roma Tor Vergata),
M. Cardillo, C. Casentini, G. Piano (INAF/IAPS), C.Pittori, F. Lucarelli,
F. Verrecchia (SSDC, and INAF/OAR),
A. Bulgarelli, V. Fioretti, N. Parmiggiani (INAF/OAS-Bologna), F. Longo
(Univ. Trieste, and INFN Trieste)
report on behalf of the AGILE Team:

In response to the LIGO/Virgo GW event S190727h at T0 = 2019-07-27 06:03:33
UTC (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 80% of the S190727h 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 S190727h
localization
region, from a minimum of 1.6E-06 erg cm^-2 to a maximum of 7.4E-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.

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 S190727h event using the 90% contour of the bayestar probability
map provided by the GW interferometers (GCN#25164
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 ). 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/S190727h.png <http://antares.in2p3.fr/GW/S190727h.png>.
Considering the location probability provided by the LIGO/Virgo collaborations, there is a
55.1% 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 2019-07-27 06:03:33 and in the 90% contour of the S190727h
event. The expected number of atmospheric background events in the region visible by ANTARES is
2.3e-04 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 1.7e-03 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.

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

The HAWC Collaboration performed a follow-up of the gravitational wave
trigger S190727h (GCN #25164
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 ). At the time of the trigger the HAWC
local zenith was oriented towards (RA, Dec) = (298 deg, 19 deg).
16% of the GW candidate sky location probability (corrected map) 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 5 deg to 44 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-06 erg/cm^2 to 8.9e-05 erg/cm^2
(6.7e-06 erg/cm^2 to 3.9e-04 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.

C. M. Hui(NASA/MSFC) reports on behalf of the Fermi-GBM Team and the
GBM-LIGO/Virgo group

For S190727h and using the initial BAYESTAR skymap, Fermi-GBM was observing
65% 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 S190727h (GCN 25164
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 ). 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=288.0, Dec=21.0 with a radius of 67.2 degrees.  We therefore set
upper limits on impulsive gamma-ray emission. Using the representative
soft, normal, and hard GRB-like templates described in arXiv:1612.02395
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 , we
set the following 3 sigma flux upper limits over 10-1000 keV (in units of
10^-7 erg/s/cm^2):
Timescale  Soft     Normal   Hard
------------------------------------
0.128 s:     3.7     5.7    14.0
1.024 s:     1.2     2.8     5.8
8.192 s:     0.6     1.1     1.9

Assuming the median luminosity distance of 2022 Mpc from the GW detection,
we estimate the following intrinsic luminosity upper limits over the 1
keV-10 MeV energy range (in units of 10^50 erg/s):
Timescale  Soft     Normal   Hard
------------------------------------
0.128 s:     3.4          4.5        18.8
1.024 s:     1.1          2.2         7.8
8.192 s:     0.5          0.9         2.5

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

Using INTEGRAL/SPI-ACS public  data  we performed a search for 
counterpart of S190727h (LVC, GCN 25164
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 ).  We found only one significant 
excess (3.6 sigma) at 4 sec and duration of 0.15 s after event time 
2019-07-27T06:03:33.98. No more credible emission found within 100 s 
after the trigger time of S190727h. The background excess variance 1.25 
around +/-500 sec around event time which is somewhat higher than usual. 
The significance of the excess will be further  investigated by chance 
coincidence analysis.

The fluence of the pulse is  574 +/- 160 counts which corresponds to 
(5.7 +/ -1.6)*10^-8 erg/cm2 at the angle of 127 degrees toward most 
probable area of localization. Assuming source distance of 2022.0 Mpc 
this corresponds to the Eiso = (2.4 +/- 0.7)*10^49 erg.

The light curve of SPI-ACS can be found at 
http://grb.rssi.ru/S190727h/S190727h_SPI-ACS_0.15s_LC.png

M. Kovacevic (INFN Perugia), E. Bissaldi (Politecnico and INFN Bari),  
S. Cutini (INFN Perugia) and F. Longo (University and INFN, Trieste)  
report on behalf of the Fermi-LAT Collaboration:

We have searched data collected by the Fermi Large Area Telescope (LAT) on
July 27, 2019, for possible high-energy (E > 100 MeV) gamma-ray emission in
spatial/temporal coincidence with the LIGO/Virgo trigger S190727h (GCN 25164
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 ).

We define "instantaneous coverage" as the integral over the region of the LIGO
probability map that is within the LAT field of view at a given a  
time, and "cumulative
coverage" as the integral of the instantaneous coverage over time.  
Fermi-LAT had
instantaneous coverage of ~69% of the LIGO probability region at the  
time of the trigger
(T0 = 2019-07-27 06:03:33.986 UTC), and reached full coverage at T0+5.4 ks.

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 1.5E-10 and 7.3E-09 [erg/cm^2/s].

The Fermi-LAT point of contact for this event is Milos Kovacevic  
(milos.kovacevic@pg.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.

S. D. Barthelmy (NASA/GSFC), A. Y. Lien (GSFC/UMBC),
D. M. Palmer (LANL), 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 (PSU),
E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift team:

We report the search results in the BAT data within T0 +/- 100 s of the
LVC event S190727h (LIGO/VIRGO Collaboration GCN Circ. 25164
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 ),
where T0 is the LVC trigger time (2019-07-27T06:03:33.985 UTC).

The center of the BAT FOV at T0 is
RA = 171.271 deg,
DEC = -3.729 deg,
and the ROLL angle is 287.727 deg.
The BAT Field of View (>10% partial coding) covers 0.05% of the integrated
LVC localization probability, and 0.04% of the galaxy convolved
probability (Evans et al. 2016).

Within T0 +/- 100 s, no significant detections (signal-to-noise ratio
>~ 5 sigma) are found in the BAT raw light curves with time bins of 64 ms,
1 s, and 1.6 s. Assuming an on-axis (100% coded) short GRB with a typical
spectrum in the BAT energy range (i.e., a simple power-law model with a
power-law index of -1.32, Lien & Sakamoto et al. 2016), the 5-sigma upper
limit in the 1-s binned light curve corresponds to a flux upper
limit (15-350 keV) of ~ 6.42 x 10^-8 erg/s/cm^2.

Also, there is no significant excess in the BAT raw light curves around the
time of the possible candidate reported by INTEGRAL at ~T0+4 s
(Minaev et al. GCN 25171
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 ), though the BAT FOV may cover different part
of the sky than the INTEGRAL FOV around this time.

Event data are available from T0-14.342 to T0-11.182. No significant
detections are found in the 15-350 keV images made using the full
event data range.

BAT retains decreased, but significant, sensitivity to rate increases for
gamma-ray events outside of its FOV. About 59.13% 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/S190727h/web/source.html

Yukei Murakami, Shaunak Modak, Keto Zhang, Thomas de Jaeger,
Benjamin Stahl, Andrew Hoffman, Nachiket Girish, WeiKang Zheng,
and Alexei V. Filippenko (UC Berkeley) report on behalf of
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-wavei
event S190727h (GCN 25164
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 ) 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 166 of them based on
their priority scores and elevation visibility, with each clear-filter
exposure time being 60 s. The first image was taken at 08:02:37, July
27th UT, about 1.98 hours after the trigger, and the last image at
12:30:34 UT. Our typical limiting mag is 19.0. No viable counterparts
were identified and the analysis is ongoing. A full list of galaxies
observed by KAIT is given below.

GladeID   UT(July20)  RA_J2000   Dec_J2000
-----------------------------------------------
G0818262  08:02:37  00:00:06.371   +53:19:13.62
G1203758  08:03:52  00:00:13.9702  +51:55:08.6556
G1076663  08:05:02  00:00:17.5322  +53:09:52.6572
G0811321  08:06:11  00:00:22.105   +53:17:40.6464
G1300914  08:07:20  00:01:38.6659  +51:52:37.2648
G0244363  08:08:30  00:01:54.217   +53:15:26.2836
G0009676  08:09:39  00:02:48.8976  +53:53:13.974
G0567217  08:10:46  00:03:13.3178  +53:52:14.9772
G0776614  08:11:56  00:03:27.0797  +56:21:05.1588
G0053858  08:13:05  00:03:31.9903  +53:26:30.876
G0749731  08:14:14  00:03:38.3064  +51:46:40.4436
G0612592  08:15:24  00:03:51.3511  +51:43:37.5348
G0876890  08:16:33  00:05:13.4796  +53:39:05.8284
G0516166  08:17:42  00:05:27.7771  +53:44:51.8424
G0573585  08:18:52  00:05:34.2828  +53:37:52.8096
G0323132  08:20:01  00:06:09.7752  +54:09:57.7944
G1012532  08:21:10  00:07:02.6165  +54:35:34.944
G1024091  08:22:19  00:08:25.2883  +54:00:01.8
G0668270  08:23:29  00:08:31.0214  +53:01:49.1628
G1337350  08:24:38  00:08:36.4001  +55:41:11.814
G1282948  08:25:47  00:09:26.4521  +52:44:31.8336
G0279085  08:26:57  00:10:38.9335  +53:25:04.0404
G1437233  08:28:06  00:10:42.0216  +54:20:54.2112
G0568420  08:29:15  00:11:21.7159  +52:31:43.7124
G1013223  08:30:25  00:11:36.8186  +53:30:52.2
G0513356  08:31:34  00:12:04.5228  +52:33:24.264
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G0248155  12:30:34  00:36:43.4292  +49:25:29.64

K. Yamaoka (Nagoya U), A. Yoshida, T. Sakamoto, 
V. Pal'shin, S. Sugita (AGU), Y. Kawakubo (LSU),
S. Nakahira (RIKEN), Y. Asaoka, S. Ozawa, S. Torii (Waseda U),
Y. Shimizu,  T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC), 
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 S190727h T0 = 2019-07-27 06:03:33.986 UT (The LIGO
Scientific Collaboration and Virgo Collaboration, GCN Circ. 25164
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 ).

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 0 % and 34 %, respectively (and 35 % credible region of the 
initial localization map was above the horizon).  The HXM and SGM fields
of view were centered at RA = 191.8 deg, Dec = 45.3 deg and 
RA = 201.2 deg, Dec = 38.2 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 high energy
trigger mode at the trigger time of S190727h, but the CAL FOV
does not have any overlap with LVC probability significance map.
The CAL FOV was centered at RA= 201.1 deg, DEC= 38.2 deg at T0.

Z. Kostrzewa-Rutkowska, D. Eappachen (SRON/RU), S. Hodgkin, A. Delgado, 
D.L. Harrison, M.van Leeuwen, G. Rixon, A. Yoldas (IoA Cambridge), P.G. Jonker
(SRON/RU) on behalf of Gaia Alerts team report the discovery of a transient
candidate within the probability skymap of  S190727h (LIGO/VIRGO
Collaboration GCN  25164
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 ):

---------------------------------------------------------------------------
Name      	TNSid    	 Date [TCB]       		RaDeg     DecDeg    AlertMag URL
----------------------------------------------------------------------------

Gaia19dfl  AT2019lyg
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        2019-07-27T17:34:08	112.70158   -56.68758  18.69
http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19dfl/
---------------------------------------------------------------------------

Note: blue transient observed within 12 hours from S190727h

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

A. Anumarlapudi (IITB), Aarthy E. (PRL), V. Bhalerao (IITB), D. Bhattacharya (IUCAA), A. R. Rao (TIFR), S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:

We have carried a search for X-ray candidates in Astrosat CZTI data in a 100 sec window around the trigger time of the BBH merger event S190727h (UTC 2019-07-27 06:03:33.000, GraceDB event). CZTI is a coded aperture mask instrument that has considerable effective area for about 29% of the entire sky, but is also sensitive to brighter transients from the entire sky. At the time of merger, Astrosat's nominal pointing is (RA=17:32:08.0 (263.033), DEC=-33:47:40.4 (-33.795)), which is 67.51 deg away from the maximum probability location. At the time of merger event, the Earth-satellite-transient angle corresponding to maximum probability location is ~ 103.71 deg and hence is not occulted by Earth in satellite's frame. In a time interval of 100 sec around the event, 81.33 % of sky locations in the 90% probability region for the event is visible in the satellite's frame and the rest of 18.67 % is occulted by earth.

CZTI data were de-trended to remove orbit-wise background variation. We then searched data from three of the four independent, identical quadrants to look for coincident spikes in the count rates. Searches were undertaken by binning the data in 0.1s, 1s, and 10s respectively. Statistical fluctuations in count rates were estimated by using data from 10 (+-5) neighbouring orbits. We selected confidence levels such that the probability of a false trigger in a 1000 sec window is 10^-4.We do not find any evidence for any hard X-ray transient in this window, in the CZTI energy range of 20-200 keV.

We convert our count rates into flux by assuming that the source spectrum is a power law with alpha = -1.0. We use a detailed mass model of the satellite to calculate the instrument response for every htm grid point that fall in 90% LIGO localization region and calculate flux limit in that direction. We get the following upper limits for source flux in the 20-200 keV band by taking a probability weighted mean of flux limit and are reported here :
  
0.1 s: flux limit= 3.32e-06 ergs/cm^2/s 
1.0 s: flux limit= 1.15e-05 ergs/cm^2/s 
10.0 s: flux limit= 1.39e-05 ergs/cm^2/s

CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project.

The LIGO Scientific Collaboration and the Virgo Collaboration report: We have conducted further analysis of the LIGO and Virgo data around the time of the compact binary coalescence (CBC) candidate S190727h (GCN 25164
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 ). Parameter estimation has been performed using LALInference [1] and a new sky map, LALInference.fits.gz, distributed via GCN Notice, is available for retrieval from the GraceDB event page: https://gracedb.ligo.org/superevents/S190727h LALInference.fits.gz is the preferred sky map at this time. The 90% credible region is 151 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 2839 +/- 655 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)