LIGO/Virgo S190720a

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 S190720a
in a time range of 1000 seconds [3] centered on the alert event time
(2019-07-20 00:00:16.747 UTC to 2019-07-20 00:16:56.747 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 S190720a 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 S190720a ranges from  0.029 to 1.080 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)

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

The HAWC Collaboration performed a follow-up of the gravitational wave
trigger S190720a. At the time of the trigger the HAWC
local zenith was oriented towards (RA, Dec) = (202.1deg, 19.1deg).
35% of the GW candidate sky location probability fell within our
observable field of view (0-45 deg zenith angle).

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

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

The sensitivity of this analysis is greatly dependent on zenith angle,
ranging from 0deg to 45deg for the area searched in this
analysis. The 5sigma detection sensitivity to a 1s (100s) burst in the
80-800GeV energy range goes from 1.2e-06 erg/cm^2 to 1.1e-04 erg/cm^2
(6.4e-06 erg/cm^2 to 5.0e-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.

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 S190720a errorbox  1846 sec after notice time and 2062 sec after trigger time at 2019-07-20 00:42:58 UT, with upper limit up to  16.4 mag. The observations began at zenit distance = 78 deg. The sun  altitude  is -36.1 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=10525

We obtain a following upper limits.  

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

    2152 | 2019-07-20 00:42:58 |         MASTER-OAFA | (  1h  8m 45.30s , -66d  6m 16.82s) |   C |   180 | 16.4 |        
    2682 | 2019-07-20 00:51:47 |         MASTER-OAFA | (  1h  3m 44.19s , -64d  6m 37.00s) |   C |   180 | 16.0 |        
    3167 | 2019-07-20 00:59:52 |         MASTER-OAFA | (  1h 22m 04.77s , -64d  6m 07.17s) |   C |   180 | 15.9 |        
    3653 | 2019-07-20 01:07:58 |         MASTER-OAFA | (  0h 55m 50.61s , -60d  6m 41.48s) |   C |   180 | 15.1 |        
    4137 | 2019-07-20 01:16:02 |         MASTER-OAFA | (  1h 22m 03.76s , -64d  6m 04.84s) |   C |   180 | 15.8 |        
    4675 | 2019-07-20 01:25:01 |         MASTER-OAFA | (  1h 11m 53.80s , -60d  6m 31.76s) |   C |   180 | 15.0 |        
    5160 | 2019-07-20 01:33:05 |         MASTER-OAFA | (  0h 21m 11.67s , -56d  7m 01.30s) |   C |   180 | 15.2 |        
    5657 | 2019-07-20 01:41:22 |         MASTER-OAFA | (  0h 20m 09.20s , -54d  6m 41.58s) |   C |   180 | 15.0 |        
    8034 | 2019-07-20 02:20:59 |         MASTER-OAFA | (  0h 33m 48.98s , -54d  6m 47.83s) |   C |   180 | 14.8 |        
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 S190720a during
real-time processing of data from LIGO Hanford Observatory (H1) and
LIGO Livingston Observatory (L1) at 2019-07-20 00:08:36.704 UTC (GPS
time: 1247616534.704). The candidate was found by the PyCBC Live [1],
SPIIR [2], MBTAOnline [3], and GstLAL [4] analysis pipelines.

S190720a is an event of interest because its false alarm rate, as
estimated by the online analysis, is 3.8e-09 Hz, or about one in 8
years. The event's properties can be found at this URL:

https://gracedb.ligo.org/superevents/S190720a

Since the time of issuing the Preliminary GCN Notice at Sat 20 Jul 19
00:11:25 UTC, several other candidate events were discovered by search
pipelines. As a result, the preferred (event) data products had to be
manually selected. This caused such preferred data products (skymap,
p_astro, em_bright), as they appear in GraceDB, to change until about
the time of issuing the Initial GCN Notice at Sat 20 Jul 19 02:01:07
UTC. At the time of issuing the Initial GCN Notice and this GCN
Circular, all data products have been finalized.

The classification of the GW signal, in order of descending
probability, is BBH (99%), Terrestrial (1%), BNS (<1%), NSBH (<1%), or
MassGap (<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
[5], distributed via GCN notice about 2 hours after the candidate. This
replaces the sky map that was sent with the Preliminary GCN Notice
about 2 minutes after the candidate.

For the bayestar.fits.gz sky map, the 90% credible region is 1461
deg2. Marginalized over the whole sky, the a posteriori luminosity
distance estimate is 1071 +/- 323 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] Nitz et al. PRD 98, 024050 (2018)
 [2] Qi Chu, PhD Thesis, The University of Western Australia (2017)
 [3] Adams et al. CQG 33, 175012 (2016)
 [4] Messick et al. PRD 95, 042001 (2017)
 [5] Singer & Price PRD 93, 024013 (2016)

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

In response to the LIGO/Virgo GW event S190720a at T0 = 2019-07-20
00:08:36.747 (UT), a preliminary analysis of the AGILE Minicalorimeter
(MCAL) triggered data found no event candidate at T0.

Three-sigma upper limits (ULs) are obtained for a 1 sec integration time at
T0 for different celestial positions within the accessible 90% c.l.
localization region (LR) of S190720a (almost 65% of the LR), from a minimum
of 1.39E-06 erg cm^-2 to a maximum of 5.02E-06 erg cm^-2 (assuming as
spectral model a single power law with photon index 1.5).

We notice an MCAL trigger event 2.53 sec after T0 in the 32 msec lightcurve
with a S/N of 5.1. We are assessing the statistical significance of this
feature.

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.

N. Kawai, M. Sugizaki (Tokyo Tech), H. Negoro (Nihon U.),
S. Sugita, M. Serino (AGU),
M. Nakajima, W. Maruyama, M. Aoki, K. Kobayashi (Nihon U.),
S. Nakahira, T. Mihara, T. Tamagawa, M. Matsuoka (RIKEN),
T. Sakamoto, H. Nishida, A. Yoshida (AGU),
Y. Tsuboi, W. Iwakiri, R. Sasaki, H. Kawai, T. Sato (Chuo U.),
M. Shidatsu (Ehime U.), M. Oeda, K. Shiraishi (Tokyo Tech),
S. Ueno, H. Tomida, M. Ishikawa, Y. Sugawara, N. Isobe, R. Shimomukai, M. Tominaga (JAXA),
Y. Ueda, A. Tanimoto, 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 S190720a at 2019-07-20 00:08:36.747 UTC (GCN 25115
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 ).

At the trigger time of S190720a, the high-voltage of MAXI/GSC was off,
and it was turned on at T0+1076 sec (+17.9 min).
The first one-orbit (92 min) scan observation with GSC after the event covered 90% 
of the 90% credible region of the bayestar skymap from 00:26:32 to 01:35:16 UTC (T0+1076 to T0+5200 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, Russia),
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 combination of INTEGRAL all-sky detectors (following [1]):
SPI/ACS, IBIS/Veto, and IBIS we have performed a search for a prompt
gamma-ray counterpart of S190720a (GCN 25115
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 ).

At the time of the event (2019-07-20 00:08:36 UTC, hereafter T0),
INTEGRAL was operating in nominal mode. The peak of the event
localization probability was at an angle of 112 deg with respect to
the spacecraft pointing axis. This orientation implies strongly
suppressed (7% of optimal) response of ISGRI, strongly suppressed (31%
of optimal) response of IBIS/Veto, and near-optimal (70% 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]), IBIS, and IBIS/Veto data.

We do not detect any significant counterparts and estimate a 3-sigma
upper limit on the 75-2000 keV fluence of 1.8e-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=3D-0.5 and Ep=3D600 keV)
occurring at any time in the interval within 300 s around T0. For a
typical long GRB spectrum (Band function with alpha=3D-1, beta=3D-2.5, and
Ep=3D300 keV), the derived peak flux upper limit is ~1.5e-07 (5.6e-08)
erg/cm^2/s at 1 s (8 s) time scale in 75-2000 keV energy range.

For the mean reported distance 1071.0 Mpc this corresponds to the
limit on the total isotropic equivalent energy in 1 s of 2.5e+49 erg
for the short GRB spectrum and for a long GRB spectrum isotropic
equivalent luminosity in 1 s (8 s) of 2.1e+49 erg/s (7.7e+48 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

[GCN OPS NOTE(20jul19): There was a format error caused by a copy-paste error
in the original submission.  Per author's request, it has been manually
reconstructed in plain text here.]

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 S190720a event using the 90% contour of the bayestar probability
map provided by the GW interferometers (GCN#25115
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  <https://gcn.gsfc.nasa.gov/gcn3/25115.gcn3
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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/S190720a.png <http://antares.in2p3.fr/GW/S190720a.png>.
Considering the location probability provided by the LIGO/Virgo collaborations, there is a
41.6% 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 2019-07-20 00:08:36 and in the 90% contour of the S190720a event.
The expected number of atmospheric background events in the region visible by ANTARES is 3.50e-04 in the +/- 500s time window.
An extended search during +/- 1 hour gives no upgoing muon neutrino candidate in coincidence with the 90% contour.
In this extended time window, an event (Time = 01:06:24, RA=200.3deg, Dec=7.6 deg) is seen outside the 99% contour, close to the ANTARES horizon.
Considering the expected number of atmospheric background events in the ANTARES upgoing field of view, this had a ~10% chance to occur.

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.

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

In response to the LIGO-Virgo GW event S190720a at T0 = 2019-07-20
00:08:36.747 (UT) a preliminary analysis of the AGILE exposure near T0
shows that the Gamma-Ray Imaging Detector (GRID) exposure covered about 44%
of the 90% c.l. localization region (LR).

We performed an analysis of the GRID data in the energy range 50 MeV - 10
GeV near T0. No candidate gamma-ray transient was detected.

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

from 8.68e-07 to 5.09e-06 erg cm^-2 sec^-1, during the time interval (T0 -
2 sec ; T0 + 2 sec);

from 3.36e-07 to 2.36e-06 erg cm^-2 sec^-1, during the time interval (T0 ;
T0 + 10 sec);

from 3.22e-08 to 2.34e-06 erg cm^-2 sec^-1, during the time interval (T0 ;
T0 + 100 sec).

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

J. Wood (NASA/MSFC) reports on behalf of the Fermi-GBM Team and the GBM-LIGO/Virgo group:

For the LIGO/Virgo detection of GW trigger S190720a (GCN 25115
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 ) and using the initial BAYESTAR skymap, Fermi-GBM was observing 73.2% of the localization probability at event time.

There was no Fermi-GBM onboard trigger around the event time of S190720a. 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.

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^-8 erg/s/cm^2):

Timescale ��Soft �� Normal �� Hard
------------------------------------
0.128 s: �� 37. �� ��57. �� �� ��110.
1.024 s: �� 13. �� ��17. �� �� ��40.
8.192 s: �� 3.2 �� ��4.9 �� �� ��9.5 

Assuming the median luminosity distance of 1071 Mpc (z=0.215) 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: �� 78.6 �� 110. �� �� 352.
1.024 s: �� 27.6 �� 32.7 �� �� 128.
8.192 s: �� 6.80 �� 9.42 �� �� 30.4

T. Sakamoto (AGU), S. D. Barthelmy (NASA/GSFC),
A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL),
A. A. Breeveld (MSSL-UCL), A. P. Beardmore (U. Leicester),
D. N. Burrows (PSU), S. Campana (INAF-OAB), S. B. Cenko (NASA/GSFC), 
G. Cusumano (INAF-IASF PA), A. D'Ai (INAF-IASFPA),
P. D'Avanzo (INAF-OAB), V. D'Elia (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 S190720a (LIGO/VIRGO Collaboration GCN Circ. 25115
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 ),
where T0 is the LVC trigger time (2019-07-20T00:08:36.704 UTC).

The center of the BAT FOV at T0 is
RA = 67.774 deg,
DEC = 0.195 deg,
and the ROLL angle is 53.680 deg.
The BAT Field of View (>10% partial coding) covers 0.00% of the integrated
LVC localization probability.

Within T0 +/- 100 s, no significant detections (signal-to-noise ratio
>~ 5 sigma) are found in the BAT raw light curves with time bins of 64 ms,                                                                                 
1 s, and 1.6 s. Assuming an on-axis (100% coded) short GRB with a typical
spectrum in the BAT energy range (i.e., a simple power-law model with a
power-law index of -1.32, Lien & Sakamoto et al. 2016), the 5-sigma upper
limit in the 1-s binned light curve corresponds to a flux upper
limit (15-350 keV) of ~ 8.66 x 10^-8 erg/s/cm^2. Note that Swift
was slewing from ~T-60 s to ~T+80 s, and thus the bump in the raw light
curve around this time is likely due to the background changes during
slew.

No event data are available within T0 +/- 100 s.

BAT retains decreased, but significant, sensitivity to rate increases for
gamma-ray events outside of its FOV. About 56.53% 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/S190720a/web/source.html

Keto Zhang, Shaunak Modak, Yukei Murakami, Thomas de Jaeger,
Benjamin Stahl, WeiKang Zheng, Emily Ma, 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-wavei
event S190720a (GCN 25115
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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 318 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 04:22:13, July
20th UT, about 4.2 hours after the trigger, and the last image at
12:09:17 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
-----------------------------------------------
G0791468  04:22:13  12:35:48.0286  +03:12:07.0884
G0125906  04:24:39  13:41:49.1419  +26:22:24.8844
G0640817  04:25:48  13:49:23.5656  +28:06:26.6076
G1812765  04:27:02  14:17:55.68    +35:27:45.612
G0768137  04:28:55  18:13:50.6616  +47:21:14.922
G0913903  04:30:04  18:14:33.5522  +45:47:17.754
G0054767  04:31:13  18:21:52.6978  +45:07:57.6588
G0899681  04:32:22  18:23:52.0385  +45:06:13.2876
G1226063  04:33:32  18:24:36.1157  +43:45:59.4756
G1138290  04:34:41  18:26:50.5298  +45:40:50.6784
G0112846  04:35:50  18:33:17.7247  +44:46:08.7456
G0986625  04:37:00  18:34:51.2182  +44:34:54.6672
G0353251  04:38:09  18:35:37.0973  +44:03:54.5868
G1042660  04:39:18  18:36:08.5106  +44:01:02.5392
G0353888  04:40:28  18:36:48.3473  +45:33:50.3424
G0306366  04:41:37  18:40:35.6616  +44:57:17.046
G0742096  04:42:46  18:44:02.417   +45:33:29.8116
G1464441  04:43:56  18:45:37.705   +44:14:28.95
G1205454  04:45:05  18:46:04.6582  +43:47:58.7616
G1333886  04:46:14  18:48:41.2207  +44:28:29.2656
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G1159909  10:59:47  21:53:17.8272  +08:57:08.1324
G1416985  11:00:56  21:53:29.3628  +07:38:41.1324
G1220897  11:02:05  21:53:32.7173  +08:35:13.1532
G0848339  11:04:24  21:54:09.331   +07:09:13.9932
G0844609  11:05:33  21:54:12.0118  +07:25:55.9992
G1141072  11:06:43  21:54:43.7182  +03:49:13.5624
G1213072  11:07:56  21:54:43.938   +08:31:04.4796
G1204885  11:09:06  21:55:00.6593  +05:20:29.5908
G1094382  11:10:15  21:55:07.0459  +07:24:42.6636
G1091392  11:11:24  21:55:28.8648  +07:18:03.2904
G1075008  11:29:05  21:56:09.4994  +06:32:05.7696
G0900540  11:30:15  21:56:10.9205  +03:36:26.3772
G0135765  11:31:24  21:56:26.5502  +06:24:09.414
G1254229  11:32:33  21:56:56.4038  +07:32:08.9592
G1069799  11:33:43  21:56:59.6558  +06:37:42.9636
G0899039  11:34:52  21:57:13.9747  +04:02:11.8068
G1476663  11:36:01  21:58:00.4176  +07:00:24.4656
G1475509  11:37:11  21:58:08.8769  +07:09:26.4816
G0436409  11:38:20  21:58:37.0973  +04:14:32.91
G0891799  11:40:37  21:59:44.8169  +02:20:24.9936
G1053187  11:41:46  22:00:50.5298  +04:45:55.7532
G0845081  11:44:04  22:01:15.1246  +01:50:50.2008
G1003217  11:45:14  22:02:03.6475  +04:17:54.1392
G1338511  11:46:23  22:02:08.8037  +06:18:44.532
G1458653  11:47:34  22:03:39.2066  +01:19:18.1632
G0321474  11:49:53  22:04:00.2124  +02:28:18.0948
G0316050  11:51:00  22:04:01.6186  +02:25:15.0996
G0771894  11:52:10  22:05:08.9429  +00:58:31.332
G1022509  11:53:19  22:05:34.3286  +01:32:42.9072
G1113127  11:54:26  22:05:37.1851  +02:11:37.9104
G0720183  12:00:13  22:07:53.628   +00:18:11.0304
G0820880  12:01:22  22:08:04.475   +01:08:06.0468
G0094454  12:09:17  22:10:33.2959  +01:31:33.2904

S. Sugita, A. Yoshida, T. Sakamoto, V. Pal'shin (AGU), 
Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), 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:

At the trigger time of the compact binary merger candidate S190720a,
T0 = 2019-07-20 00:08:36.704 UT (The LIGO Scientific Collaboration 
and Virgo Collaboration, GCN Circ. 25115
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 ), the CALET Gamma-ray 
Burst Monitor (CGBM) high voltages were off (from T0-4 min to 
T0+17 min).

The CALET Calorimeter (CAL) was operating in the high energy
trigger mode at the trigger time of S190720a. Using the CAL data,
we have searched for gamma-ray events in the 10-100 GeV
band from -60 sec to +60 sec from the GW trigger time and
found no candidates.
The 90% upper limit of CAL is 3.0x10^-5 erg/cm^2/s (10-100 GeV) when
the summed LIGO-Virgo probability reaches 25%.
The CAL FOV was centered at RA = 49.7 deg and DEC = -32.1 deg at T0.

M. Axelsson (KTH and Stockholm Univ.) reports on behalf of the Fermi-LAT Collaboration:

We have searched data collected by the Fermi Large Area Telescope (LAT) on July 20, 2019, for possible high-energy (E > 100 MeV) gamma-ray emission in spatial/temporal coincidence with the LIGO/Virgo trigger S190720a (GCN 25115
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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 ~45% of the LIGO probability region at the time of the trigger (T0 = 2019-07-20 00:08:36.704 UTC), and reached full coverage at T0+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 1.4E-10 and 3.9E-09 [erg/cm^2/s].

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

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

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

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

Alert: LIGO/Virgo S190720a (GCN #25115
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 )
StartTime (UT):               2019-07-20T13:52:48.017       
EndTime (UT):                 2019-07-20T14:48:48.031       
Skycover (Square Degree):     135.0   
Telescope FoV (Square Degree):9.0     
#id CentRA(D) CentDEC(D) LimiteMag3_sig 5_sig 10_sig Filter 
  1 231.208405  43.572357    -	     21.204   18.323   SR
  2 242.761490  46.336327   21.949   21.134   18.424   SR
  3 242.799225  43.565426   22.074   21.229   18.375   SR
  4 228.608490  40.790733    -	     21.204   18.483   SR
  5 221.265320  40.808392   21.856   21.045   18.350   SR
  6 231.208405  43.572357    -       21.204   18.323   SR
  7 242.761490  46.336327   21.949   21.134   18.424   SR
  8 242.799225  43.565426   22.074   21.229   18.375   SR
  9 228.608490  40.790733    -       21.204   18.483   SR
 10 221.265320  40.808392   21.856   21.045   18.350   SR
 11 231.208405  43.572357    -       21.204   18.323   SR
 12 242.761490  46.336327   21.949   21.134   18.424   SR
 13 242.799225  43.565426   22.074   21.229   18.375   SR
 14 228.608490  40.790733    -       21.204   18.483   SR
 15 221.265320  40.808392   21.856   21.045   18.350   SR

The new resulte will available at http://www.cneost.org/opem/list.php?gdate=2019-07-20

The LIGO Scientific Collaboration and the Virgo Collaboration report:


We have re-analyzed LIGO and Virgo data around the time of the compact
binary coalescence (CBC) candidate S190720a (GCN 25115
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 ). Parameter
estimation has been performed using LALInference [1] and a new sky
map, LALInference.offline.fits.gz, is available for retrieval from the
GraceDB event page:


https://gracedb.ligo.org/superevents/S190720a/


This is currently the preferred skymap. For the LALInference.offline.fits.gz 
sky map, the 90% credible region is 443 deg2.
Marginalized over the whole sky, the a posteriori luminosity
distance estimate is 869 +/- 283 Mpc (a posteriori mean +/- standard
deviation). This is the preferred sky map at this time. The LALInference 
skymap is generated using data from three detectors, while the sky map
shared in GCN 25115
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 , was generated from data obtained from two detectors.
This partly contributed to the better localization.


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)

J. Swift, Y. Yin (Thacher School Observatory), C. D. Kilpatrick, J. S. Brown, D. A. Coulter, G. Dimitriadis, R. J. Foley, T. Hung, D. O. Jones, C. Rojas-Bravo, M. R. Siebert, K. Siellez (UCSC)

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

in the process of following up the localization region of LIGO/Virgo event S190720a (GCN 25138
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 ), we observed the following fields for 300s each in r-band with the 0.7-m Thacher telescope at the Thacher School Observatory. The localization region was provided by the LIGO/Virgo collaboration in the LALinference map of July 22 17:43:30. All Thacher observations were performed on UT 2019 Jul 23.  The approximate center of each image is noted in the table below, and the field of view is a 21 arcmin x 21 arcmin rectangle.  We note the approximate 3-sigma limiting magnitude of each image.

Comparing our images to PS1 r-band images of the same fields, we did not detect any transient sources.

RA (J2000)  | Dec (J2000) | MJD         | Limiting Magnitude
19:45:50.18 | +35:28:46.2 | 58687.34652 |    20.4
19:55:39.26 | +37:12:37.4 | 58687.35060 |    20.1
19:54:27.91 | +37:33:24.8 | 58687.35459 |    19.8
19:52:21.53 | +38:14:58.9 | 58687.35855 |    20.2
19:55:01.25 | +37:54:12.6 | 58687.36250 |    20.0
19:56:12.58 | +37:33:26.6 | 58687.36645 |    18.8
19:53:15.86 | +37:54:13.0 | 58687.37039 |    19.0
19:57:23.21 | +37:12:40.3 | 58687.37435 |    20.1
19:56:49.44 | +36:51:54.7 | 58687.37831 |    20.5
19:50:35.76 | +38:15:01.4 | 58687.38227 |    20.7
19:51:30.55 | +37:54:15.1 | 58687.38623 |    20.6
19:52:42.91 | +37:33:27.7 | 58687.39022 |    20.6
19:53:54.65 | +37:12:41.8 | 58687.39418 |    20.6
19:55:05.59 | +36:51:56.2 | 58687.39814 |    20.3
19:48:50.04 | +38:15:02.2 | 58687.40209 |    20.2
19:49:45.19 | +37:54:15.8 | 58687.40606 |    19.7
19:50:58.03 | +37:33:29.5 | 58687.41002 |    18.5
19:52:10.22 | +37:12:43.6 | 58687.41397 |    18.9
19:53:21.70 | +36:51:57.2 | 58687.41792 |    17.1
19:54:32.47 | +36:31:12.0 | 58687.42186 |    16.9

Please direct all communication related to this circular to Charlie Kilpatrick (cdkilpat@ucsc.edu).

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 S190720a (UTC 2019-07-20 00:08:36.000, 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=2:27:09.6 (36.790), DEC=33:33:21.1 (33.556)), which is 77.17 deg away from the maximum probability location. At the time of merger event, the Earth-satellite-transient angle corresponding to maximum probability location is ~ 82.09 deg and hence is not occulted by Earth in satellite's frame. In a time interval of 100 sec around the event, 76.74 % of sky locations in the 90% probability region for the event is visible in the satellite's frame and the rest of 23.26 % 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= 5.98e-07 ergs/cm^2/s 
1.0 s: flux limit= 1.91e-06 ergs/cm^2/s 
10.0 s: flux limit= 2.41e-06 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.