LIGO/Virgo S190828l

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

The HAWC Collaboration performed a follow-up of the gravitational wave
trigger S190828l. At the time of the trigger the HAWC
local zenith was oriented towards (RA, Dec) = (342.5 deg, 18.9 deg).
21% 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 0.9 deg to 45.0 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 1.1e-04 erg/cm^2
(6.5e-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.

The LIGO Scientific Collaboration and the Virgo Collaboration report:


We identified the compact binary merger candidate S190828l during
real-time processing of data from LIGO Hanford Observatory (H1), LIGO
Livingston Observatory (L1), and Virgo Observatory (V1) at 2019-08-28
06:55:09.887 UTC (GPS time: 1251010527.887). The candidate was found
by the GstLAL [1], MBTAOnline [2], SPIIR [3], and PyCBC Live [4]
analysis pipelines.

Note that S190828l and S190828j (GCN 25497
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 ) are distinct events that
occurred 21 minutes apart.

S190828l is an event of interest because its false alarm rate, as
estimated by the online analysis, is 4.6e-11 Hz, or about one in 700
years. The event's properties can be found at this URL:

https://gracedb.ligo.org/superevents/S190828l

The classification of the GW signal, in order of descending
probability, is BBH (>99%), Terrestrial (<1%), BNS (<1%), MassGap
(<1%), or NSBH (<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 22 minutes after the candidate

For the bayestar.fits.gz sky map, the 90% credible region is 948 deg2.
Marginalized over the whole sky, the a posteriori luminosity distance
estimate is 1609 +/- 426 Mpc (a posteriori mean +/- standard
deviation).

The localizations of S190828j and S190828l strongly resemble each
other. This is not unexpected for events occurring at similar times
because the detector sensitivity antenna patterns rotate with the
Earth. The two localizations are definitely disjoint: their
prevailing triangulation annuli are separated by over 10 degrees.

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

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 S190828l (GCN 25503
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 ).

At the time of the event (2019-08-28 06:55:09 UTC, hereafter T0), 
INTEGRAL was operating in nominal mode. The peak of the event 
localization probability was at an angle of 87 deg with respect to the 
spacecraft pointing axis. This orientation implies strongly suppressed 
(9.1% of optimal) response of ISGRI, strongly suppressed (28% of 
optimal) response of IBIS/Veto, and near-optimal (83% 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 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=-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 (5.6e-08) 
erg/cm^2/s at 1 s (8 s) time scale in 75-2000 keV energy range.

For the mean reported distance 1609.0 Mpc this corresponds to the limit 
on the total isotropic equivalent energy in 1 s of 5.5e+49 erg for the 
short GRB spectrum and for a long GRB spectrum isotropic equivalent 
luminosity in 1 s (8 s) of 4.7e+49 erg/s (1.7e+49 erg/s)

We report for completeness and in order of FAP, all excesses identified 
in the search region. We find: 6 likely background excesses:

scale | T | S/N | luminosity ( x 1e+50 erg/s) | FAP
1.1 | -94.7 | 3.9 | 10.1 +/- 3.08 +/- 5.79 | 0.32
0.4 | -31.2 | 3.7 | 16.1 +/- 5.12 +/- 9.27 | 0.368
0.45 | 51.4 | 3.7 | 15.2 +/- 4.83 +/- 8.74 | 0.594
0.8 | -33.8 | 3.1 | 9.37 +/- 3.61 +/- 5.4 | 0.809
4.3 | 249 | 3.2 | 4.16 +/- 1.55 +/- 2.4 | 0.936
1.3 | -71.8 | 3.1 | 7.53 +/- 2.83 +/- 4.34 | 0.957

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

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 S190828l event using the 90% contour of the Initial bayestar probability
map provided by the GW interferometers (GCN#25503
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  <https://gcn.gsfc.nasa.gov/gcn3/25503.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/S190828l_Initial.png <http://antares.in2p3.fr/GW/S190828l_Initial.png>.
Considering the location probability provided by the LIGO/Virgo collaborations, there is a
56.8% 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 2019-08-28 06:55:09 and in the 90% contour of the S190828l
event. The expected number of atmospheric background events in the region visible by ANTARES is
2.80e-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 2.02e-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.

F. Longo (Univ. Trieste, and INFN Trieste), F. Verrecchia, C. Pittori
(SSDC, and INAF/OAR), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata),
M. Cardillo, C. Casentini, G. Piano, A. Ursi (INAF/IAPS), F. Lucarelli
(SSDC, and INAF/OAR), 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 S190828l at T0 = 2019-08-28
06:55:09 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 50% of the S190828l 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 S190828l localization region, from a minimum of
1.83E-06 erg cm^-2 to a maximum of 6.33E-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.

H. Negoro (Nihon U.), M. Serino, S. Sugita (AGU), 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 S190828l at 2019-08-28 06:55:09.886 UTC (GCN 25503
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 ). 

At the trigger time of S190828l, the high-voltage of MAXI/GSC was off, 
and it was turned on at T0+387 sec (+6.5 min). 
The first one-orbit (92 min) scan observation with GSC after the event covered 94% 
of the 90% credible region of the bayestar skymap from 07:01:46 to 08:10:26 UTC (T0+397 to T0+4517 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.

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 S190828l errorbox  1606 sec after notice time and 3022 sec after trigger time at 2019-08-28 07:45:31 UT, with upper limit up to  16.6 mag. The observations began at zenit distance = 84 deg. The sun  altitude  is -41.4 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=10739

We obtain a following upper limits.  

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

    3113 | 2019-08-28 07:45:31 |         MASTER-OAFA | (09h 43m 48.516s , -49d 48m 33.56s) |   C |   180 | 14.8 |        
    6722 | 2019-08-28 08:45:40 |         MASTER-OAFA | (09h 37m 17.654s , -51d 55m 37.22s) |   C |   180 | 16.6 |        
    6943 | 2019-08-28 08:49:22 |         MASTER-OAFA | (09h 37m 19.541s , -51d 55m 31.84s) |   C |   180 | 15.8 |        
Filter C is a clear (unfiltred) band. 


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

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
S190828l
 in a time range of 1000 seconds [3] centered on the alert event time
(2019-08-28 06:46:49.887 UTC to 2019-08-28 07:03:29.887 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
S190828l calculated from the map circulated in the 2-Initial 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 S190828l ranges from  0.030 to 1.000 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)

F. Longo (Univ. Trieste, and INFN Trieste), F. Verrecchia, C. Pittori
(SSDC, and INAF/OAR), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata),
M. Cardillo, C. Casentini, G. Piano, A. Ursi (INAF/IAPS), F. Lucarelli
(SSDC, and INAF/OAR), 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 S190828l at T0 = 2019-08-28
06:55:09.887 UT a preliminary analysis of the AGILE exposure at T0 shows
that the Gamma-Ray Imaging Detector (GRID) exposure covered less than 10%
of the 90% c.l. localization region (LR; around 40% of 90% c.l. LR is
occulted by Earth).

We performed an analysis of the GRID data in the energy range 50 MeV -
10 GeV over time intervals before and after T0, where good exposure of
the S190828l 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 3e-08 to 2.e-07 erg cm^-2 s^-1, with exposure of about 50% of
the LR over the time interval ( T0 - 100s ; T0 + 0s );
from 8e-08 to 7e-08 erg cm^-2 s^-1, with exposure of about 50% of the
LR over the time interval ( T0 + 200s ; T0 + 300s );

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

P. Veres (UAH) reports on behalf of the Fermi-GBM Team and the
GBM-LIGO/Virgo group:

For S190828l and using the initial bayestar skymap, Fermi-GBM was observing
29% 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 S190828l (GCN 25503
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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.

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 erg/s/cm^2):

Timescale  Soft     Normal   Hard
------------------------------------
0.128 s:   1.8e-07  2.3e-07  5.0e-07
1.024 s:   6.4e-08  1.0e-07  2.1e-07
8.192 s:   2.7e-08  3.5e-08  7.7e-08

Assuming the median luminosity distance of 1609 Mpc (z=0.31) from the GW
detection, we estimate the following intrinsic luminosity upper limits over
the 1 keV-10 MeV energy range (in units of 10^49 erg/s):

Timescale  Soft     Normal   Hard
------------------------------------
0.128 s:     8.9          10         37
1.024 s:     3.2          4.4        16
8.192 s:     1.3          1.5        5.7

A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (NASA/GSFC),
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), D. B. Malesani (DTU Space),
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 S190828l (LIGO/VIRGO Collaboration GCN Circ. 25503
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 ),
where T0 is the LVC trigger time (2019-08-28T06:55:09.887 UTC).

The center of the BAT FOV at T0 is
RA = 323.901 deg,
DEC = 47.455 deg,
The roll angle is 351.941 deg.
The BAT Field of View (>10% partial coding) covers 21.29% of the integrated
LVC localization probability, and 21.76% 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 ~ 7.29 x 10^-8 erg/s/cm^2.

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 4.86% 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/S190828l/web/source_public.html

Y. Shimizu (Kanagawa U), A. Yoshida, T. Sakamoto, V. Pal'shin, 
S. Sugita (AGU),  Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), 
S. Nakahira (RIKEN), Y. Asaoka, S. Ozawa, S. Torii (Waseda U), 
T. Tamura (Kanagawa U), N. Cannady (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 S190828l T0 = 2019-08-28 06:55:09.887 UT (The LIGO
Scientific Collaboration and Virgo Collaboration, GCN Circ. 25503
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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 5 % and 41 %, respectively (and 79 % credible region 
of the initial localization map was above the horizon).  The HXM and 
SGM fields of view were centered at RA = 109.4 deg, Dec = 60.9 deg
and RA = 107.0 deg, Dec = 51.0 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 S190828l, but the CAL FOV 
does not have any overlap with the high probability localization region.
The CAL FOV was centered at RA = 106.9 deg, DEC = 51.0 deg at T0.

F. Piron (CNRS/IN2P3/LUPM), N. Omodei (Stanford Univ.), F. Longo (Univ. and INFN Trieste), M. Arimoto (Kanazawa Univ.), D. Kocevski (NASA/MSFC), M. Axelsson (KTH and Stockholm Univ.) 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 Aug 28, 2019, for possible high-energy (E > 100 MeV) gamma-ray emission in spatial/temporal coincidence with the LIGO/Virgo trigger S190828l (GCN 25503
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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 22% of the LIGO probability region at the time of the trigger (T0 = 2019-08-28 06:55:09.887 UTC), and reached 100% cumulative coverage after 5.1 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 1.2E-10 and 2.7E-08 [erg/cm^2/s].

The Fermi-LAT point of contact for this event is Frederic Piron (piron@in2p3.fr<mailto:piron@in2p3.fr>).

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.

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 
S190828l event (GCN #25503
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 ), trigger time 2019-08-28T06:55:09.887 UTC. 
At T0, about 77% 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=145 deg, DEC=-50 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:   2.5e-07 erg cm^-2
10 s:  1.1e-06 erg cm^-2

Band model 2 (alpha=-1.0, beta=-2.3, Ep=230 keV):
1 s:   4.0e-07 erg cm^-2
10 s:  1.8e-06 erg cm^-2

Band model 3 (alpha=-0.0, beta=-1.5, Ep=1000 keV):
1 s:   8.8e-07 erg cm^-2
10 s:  2.8e-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.

Shaunak Modak, Sergiy Vasylyev, Thomas de Jaeger, Keto D. Zhang,
WeiKang Zheng, Andrew Hoffman, Benjamin E. Stahl, Yukei Murakami,
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 S190828l (GCN 25503
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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 59 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 11:44:07, Aug.
29th UT, about 28.8 hours after the trigger, and the last image at
12:57:58 UT. Our typical limiting mag is 18.5. No viable counterparts
were identified and the analysis is ongoing. A full list of galaxies
observed by KAIT is given below.

GladeID   UT(Aug29)  RA_J2000   Dec_J2000
-----------------------------------------------
G0595607  11:44:07  03:00:30.444   +49:21:13.3848
G0768405  11:45:18  03:03:32.1653  +49:37:19.7688
G0777619  11:46:32  03:03:40.4251  +51:34:31.8144
G0672859  11:47:43  03:05:05.8877  +50:19:24.096
G0738775  11:48:59  03:06:24.3511  +52:34:54.9264
G0599454  11:50:08  03:10:38.0302  +48:52:10.7328
G0559089  11:51:20  03:27:21.6842  +49:59:01.0032
G0695101  11:52:31  03:37:07.4249  +49:03:08.7444
G0747552  11:53:52  05:11:53.8622  +45:37:14.2356
G0336853  11:55:02  05:13:42.0134  +46:00:58.4064
G0526083  11:56:11  05:16:39.1992  +45:34:27.9696
G1097965  11:57:20  05:17:19.7606  +42:05:05.9568
G0161517  11:58:30  05:17:54.7723  +42:24:03.852
G0626286  11:59:39  05:20:14.154   +43:18:21.4056
G1302293  12:00:48  05:22:14.6686  +41:28:19.902
G0736602  12:01:58  05:24:13.1177  +42:20:18.1356
G0886051  12:03:08  05:25:17.7338  +45:24:10.6488
G1147141  12:04:17  05:25:40.6294  +41:41:53.0124
G1243574  12:05:27  05:25:51.5258  +43:10:11.5536
G1231909  12:06:36  05:26:01.8293  +43:22:56.6292
G1200246  12:07:51  05:26:30.4121  +40:26:56.0076
G0606566  12:09:03  05:27:25.0322  +45:50:49.0344
G0186139  12:10:13  05:27:27.2882  +41:59:04.848
G1414478  12:11:22  05:27:33.9991  +46:11:58.0128
G0926148  12:12:32  05:27:37.8094  +44:08:45.9852
G0934140  12:13:43  05:27:40.9222  +46:09:53.9604
G0284079  12:14:52  05:28:03.9442  +43:09:14.1516
G0386281  12:16:02  05:28:04.477   +43:39:18.162
G1287779  12:17:13  05:28:15.5364  +43:04:08.1264
G1402290  12:18:22  05:29:42.7094  +45:30:00.8928
G0344496  12:25:25  05:29:45.3058  +43:32:20.7348
G0601049  12:26:34  05:29:55.4719  +44:34:38.8056
G0069319  12:27:48  05:30:02.8692  +44:11:51.8172
G0957486  12:28:57  05:30:03.521   +44:38:15.828
G0917178  12:30:13  05:30:04.8065  +41:54:08.2584
G1464030  12:31:22  05:30:04.931   +44:44:55.824
G1121082  12:32:31  05:30:43.9013  +42:25:50.6928
G0841668  12:33:41  05:30:49.9438  +41:12:59.1228
G1331307  12:34:50  05:30:56.1384  +42:40:15.6612
G1190621  12:35:59  05:31:05.7972  +40:40:39.4608
G1122787  12:37:09  05:31:17.3767  +41:54:59.4972
G0412661  12:38:18  05:31:24.0014  +45:52:02.6292
G1138379  12:39:27  05:31:38.6134  +41:45:04.8492
G1027891  12:40:37  05:31:38.9887  +42:30:19.5696
G1216616  12:41:46  05:31:42.2717  +40:59:51.8856
G1385195  12:42:53  05:31:59.0496  +40:46:44.9472
G1101923  12:44:03  05:32:01.8403  +41:39:29.9304
G1125001  12:45:12  05:32:05.5903  +41:40:03.918
G0747978  12:46:20  05:32:17.9518  +42:30:28.2348
G1017116  12:47:30  05:32:37.8588  +45:00:12.114
G1146557  12:48:39  05:33:00.1997  +41:40:23.5164
G0957979  12:49:48  05:33:11.9054  +44:45:11.3292
G1284321  12:50:58  05:33:34.1162  +47:04:33.3408
G0965263  12:52:07  05:33:37.11    +44:33:03.3192
G1417780  12:53:14  05:34:17.5286  +44:35:02.3028
G1471417  12:54:28  05:34:19.9183  +41:45:17.6184
G1176015  12:55:39  05:34:25.2338  +46:23:48.894
G1370730  12:56:48  05:34:56.1785  +44:41:19.86
G1422126  12:57:58  05:35:16.5382  +44:26:24.09

S. Antier (APC), C. Lachaud (APC), N. Christensen (Artemis), B. Gendre 
(OzGrav-UWA), N. Ismayilov (SHAO), M. Boer (Artemis), L. Eymar 
(Artemis), A. Klotz (IRAP), K. Noysena (Artemis, IRAP), S. Basa (LAM), 
D. Corre (LAL), M. Coughlin (Caltech), D. Coward (OzGrav-UWA), J.G. 
Ducoin (LAL), P. Hello (LAL), N. Leroy (LAL), D. Turpin (NAOC), X. Wang 
(THU) report on behalf of the TAROT network and GRANDMA collaborations.

We performed tiled observations of the LIGO/Virgo event S190828l with 
the TAROT-Chili (TCH), TAROT-Calern (TCA) and TAROT-Reunion (TRE) 
telescopes operating in the visible located respectively at La Silla ESO 
Observatory (LaS/ESO), Calern site at the Cote d'Azur Observatory and 
Les Makes astronomical Observatory.


The observation started for TCH on 08/28/19 08:08:26 UTC which 
corresponds to approximately 74 minutes after the GW trigger time.

We performed the following tiled observations :

+-------+------------+------------+---------+---------+---------+
| Tele  | TStart     | TEnd       | RA      | DEC     |   Proba |
| scope | [UTC]      | [UTC]      | [deg]   | [deg]   |     [%] |
|-------+------------+------------+---------+---------+---------|
|  TCH  | 2019-08-28 | 2019-08-30 | 155.236 | -61.777 |     0.5 |
|       | 08:08:26   | 09:29:11   |         |         |         |
|  TCH  | 2019-08-28 | 2019-08-29 | 157.656 | -63.595 |     0.5 |
|       | 08:15:15   | 23:35:28   |         |         |         |
|  TCH  | 2019-08-28 | 2019-08-30 | 149.185 | -58.141 |     0.5 |
|       | 08:22:03   | 09:41:21   |         |         |         |
|  TCH  | 2019-08-28 | 2019-08-30 | 159.192 | -61.777 |     0.5 |
|       | 08:28:51   | 09:48:09   |         |         |         |
|  TCH  | 2019-08-28 | 2019-08-30 | 160.538 | -59.959 |     0.3 |
|       | 09:06:48   | 00:27:25   |         |         |         |
|  TCH  | 2019-08-28 | 2019-08-29 | 163.148 | -61.777 |     0.3 |
|       | 08:51:18   | 09:33:23   |         |         |         |
|  TCH  | 2019-08-28 | 2019-08-30 | 153.421 | -63.595 |     0.3 |
|       | 08:58:06   | 00:39:41   |         |         |         |
|  TCH  | 2019-08-28 | 2019-08-28 | 152.715 | -58.141 |     0.8 |
|       | 09:29:56   | 09:58:42   |         |         |         |
|  TCH  | 2019-08-28 | 2019-08-30 | 153.115 | -59.959 |     0.7 |
|       | 09:36:44   | 09:08:47   |         |         |         |
|  TCH  | 2019-08-28 | 2019-08-30 | 156.244 | -58.141 |     0.6 |
|       | 10:14:23   | 09:22:23   |         |         |         |
|  TCH  | 2019-08-28 | 2019-08-30 | 151.28  | -61.777 |     0.3 |
|       | 08:37:52   | 00:20:37   |         |         |         |
|  TCH  | 2019-08-28 | 2019-08-30 | 166.126 | -63.595 |     0.2 |
|       | 23:39:52   | 00:46:29   |         |         |         |
|  TCH  | 2019-08-28 | 2019-08-30 | 167.45  | -65.414 |     0.2 |
|       | 23:46:40   | 00:53:17   |         |         |         |
|  TCH  | 2019-08-29 | 2019-08-30 | 156.826 | -59.959 |     0.6 |
|       | 00:39:07   | 09:15:35   |         |         |         |
|  TCH  | 2019-08-29 | 2019-08-30 | 162.95  | -65.414 |     0.4 |
|       | 01:37:16   | 00:13:48   |         |         |         |
|  TCH  | 2019-08-29 | 2019-08-30 | 153.95  | -65.414 |     0.2 |
|       | 00:01:13   | 08:35:31   |         |         |         |
|  TCH  | 2019-08-29 | 2019-08-30 | 158.45  | -65.414 |     0.4 |
|       | 01:24:45   | 10:01:45   |         |         |         |
|  TCH  | 2019-08-29 | 2019-08-29 | 149.404 | -59.959 |     0.4 |
|       | 09:00:58   | 09:07:28   |         |         |         |
|  TCH  | 2019-08-29 | 2019-08-30 | 161.49  | -67.232 |     0.2 |
|       | 09:52:35   | 01:00:05   |         |         |         |
|  TCH  | 2019-08-29 | 2019-08-30 | 161.891 | -63.595 |     0.5 |
|       | 01:17:57   | 09:54:57   |         |         |         |
|-------+------------+------------+---------+---------+---------|
|  TCA  | 2019-08-28 | 2019-08-28 | -0.95   | 40.372  |     0.3 |
|       | 19:25:55   | 19:32:26   |         |         |         |
|  TCA  | 2019-08-28 | 2019-08-29 | 356.118 | 39.897  |     0.2 |
|       | 19:32:44   | 00:38:48   |         |         |         |
|  TCA  | 2019-08-28 | 2019-08-30 | 20.793  | 50.125  |     0.2 |
|       | 19:39:35   | 01:45:21   |         |         |         |
|  TCA  | 2019-08-28 | 2019-08-28 | 358.467 | 42.228  |     0.2 |
|       | 20:11:14   | 20:17:43   |         |         |         |
|  TCA  | 2019-08-28 | 2019-08-28 | 5.915   | 42.703  |     0.1 |
|       | 20:18:03   | 20:24:35   |         |         |         |
|  TCA  | 2019-08-28 | 2019-08-30 | 21.606  | 51.981  |     0.1 |
|       | 20:24:55   | 02:30:44   |         |         |         |
|  TCA  | 2019-08-28 | 2019-08-29 | 6.056   | 44.558  |     0.1 |
|       | 21:16:04   | 22:22:35   |         |         |         |
|  TCA  | 2019-08-28 | 2019-08-29 | 22.768  | 48.27   |     0.1 |
|       | 21:22:55   | 22:29:26   |         |         |         |
|  TCA  | 2019-08-28 | 2019-08-29 | 3.503   | 44.558  |     0.1 |
|       | 21:29:46   | 22:36:15   |         |         |         |
|  TCA  | 2019-08-28 | 2019-08-30 | 3.433   | 42.703  |     0.2 |
|       | 22:21:49   | 01:59:03   |         |         |         |
|  TCA  | 2019-08-28 | 2019-08-28 | 0.95    | 42.703  |     0.2 |
|       | 22:28:37   | 22:35:08   |         |         |         |
|  TCA  | 2019-08-28 | 2019-08-28 | 4.357   | 40.847  |     0.2 |
|       | 22:35:30   | 22:42:00   |         |         |         |
|  TCA  | 2019-08-28 | 2019-08-28 | 18.655  | 51.981  |     0.1 |
|       | 23:26:38   | 23:33:08   |         |         |         |
|  TCA  | 2019-08-28 | 2019-08-29 | 355.985 | 41.753  |     0.1 |
|       | 23:33:27   | 19:39:36   |         |         |         |
|  TCA  | 2019-08-28 | 2019-08-29 | 23.627  | 50.125  |     0.1 |
|       | 23:40:17   | 19:44:12   |         |         |         |
|  TCA  | 2019-08-29 | 2019-08-30 | 1.941   | 40.847  |     0.2 |
|       | 00:46:00   | 01:52:12   |         |         |         |
|  TCA  | 2019-08-29 | 2019-08-30 | 20.041  | 48.27   |     0.1 |
|       | 01:31:03   | 02:37:35   |         |         |         |
|  TCA  | 2019-08-29 | 2019-08-29 | 17.958  | 50.125  |     0.1 |
|       | 01:37:52   | 21:42:04   |         |         |         |
|  TCA  | 2019-08-29 | 2019-08-29 | 353.702 | 39.897  |     0.1 |
|       | 21:44:38   | 21:51:09   |         |         |         |
|-------+------------+------------+---------+---------+---------|
|  TRE  | 2019-08-28 | 2019-08-28 | 331.034 | 8.182   |     0.4 |
|       | 21:08:23   | 21:14:51   |         |         |         |
|  TRE  | 2019-08-28 | 2019-08-28 | 338.571 | 16.364  |     0.4 |
|       | 21:21:39   | 21:28:07   |         |         |         |
|  TRE  | 2019-08-28 | 2019-08-29 | 354.857 | 36.818  |     1.2 |
|       | 22:02:37   | 20:39:07   |         |         |         |
|  TRE  | 2019-08-28 | 2019-08-29 | 330     | 16.364  |     0.3 |
|       | 23:57:44   | 00:04:12   |         |         |         |
|  TRE  | 2019-08-29 | 2019-08-29 | 350.27  | 32.727  |     1.4 |
|       | 00:26:17   | 00:32:45   |         |         |         |
|  TRE  | 2019-08-29 | 2019-08-29 | 342     | 24.545  |     1.1 |
|       | 00:39:00   | 00:45:28   |         |         |         |
|  TRE  | 2019-08-29 | 2019-08-29 | 330.698 | 12.273  |     0.7 |
|       | 16:23:40   | 16:30:08   |         |         |         |
|  TRE  | 2019-08-29 | 2019-08-29 | 333.659 | 20.455  |     0.5 |
|       | 16:41:25   | 16:43:25   |         |         |         |
|  TRE  | 2019-08-29 | 2019-08-29 | 345.974 | 28.636  |     1.1 |
|       | 20:45:52   | 20:52:26   |         |         |         |
+-------+------------+------------+---------+---------+---------+


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 refers to the 2D spatial probability 
of the GW skymap enclosed in a given tile. Each tile is  1.9x1.9 degrees 
for TCA and TCH and 4.2x4.2 degrees for TRE. The coordinating 
observations cover about 18% of the cumulative probability of the 
bayestar skymap available on Aug 28, 2019 07:17:33 UTC. The typical 
limiting magnitude 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/JF7J7CIdlrc7qs1

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 
telescope  are available on the GRANDMA web pages
or on
http://tarot.obs-hp.fr/.

J. Y. Wei (NAOC), X. H. Han (NAOC), N. Dagoneau (CEA/AIM), J. Wang (GXU),
N. Leroy (CNRS/LAL)

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

We observed 16 sky regions (total: 2400 square degrees with overlaps)
to cover the skymap of the advanced LIGO/Virgo trigger S190828l,
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 9.5% prior probability
that the 16 observed and processed regions contain the true location of
the source.  The images were taken between ~5 hours and ~12 hours after
the event trigger time.

The coordinates of the 16 sky regions and observation times are listed
below:

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

1 00:22:12.55 35:47:18.96 2019-08-28 14:58:26 2019-08-28 15:16:39 JFOV 
2 00:16:40.40 47:47:40.20 2019-08-28 14:59:15 2019-08-28 15:17:03 JFOV 
3 00:05:09.89 34:55:44.40 2019-08-28 15:00:32 2019-08-28 15:17:08 JFOV 
4 01:11:41.69 47:17:32.64 2019-08-28 15:07:01 2019-08-28 15:17:08 JFOV 
5 01:43:32.26 64:07:03.00 2019-08-28 13:53:25 2019-08-28 16:51:08 JFOV 
6 00:07:40.03 51:45:14.40 2019-08-28 16:41:24 2019-08-28 16:44:15 JFOV 
7 00:13:04.03 64:02:39.84 2019-08-28 17:05:25 2019-08-28 17:22:48 JFOV 
8 02:38:20.69 47:18:19.08 2019-08-28 17:04:13 2019-08-28 17:22:03 JFOV 
9 01:31:55.32 34:55:32.16 2019-08-28 17:09:05 2019-08-28 17:22:03 JFOV 
10 21:55:06.96 10:04:51.24 2019-08-28 16:04:03 2019-08-28 16:20:14 JFOV 
11 21:55:29.52 -1:58:15.89 2019-08-28 16:00:25 2019-08-28 16:20:14 JFOV 
12 21:59:13.44 48:02:44.52 2019-08-28 13:40:52 2019-08-28 14:06:20 JFOV 
13 22:05:10.08 34:10:09.48 2019-08-28 12:08:19 2019-08-28 19:00:58 JFOV
14 23:07:07.68 09:08:42.00 2019-08-28 17:49:12 2019-08-28 17:54:27 JFOV 
15 23:44:10.08 13:41:13.56 2019-08-28 18:09:03 2019-08-28 18:26:03 JFOV 
16 00:58:52.99 30:19:11.28 2019-08-28 17:25:15 2019-08-28 17:53:12 JFOV

The sky coverage map is available at: 
http://cmm.svom.cn/gwpub/O3/S190828l/S190828l.png
(user:svomo3 pwd:gwo3)

The weather conditions were hazy 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.

The LIGO Scientific Collaboration and the Virgo Collaboration report:

We have conducted further analysis of the data from LIGO Hanford
Observatory (H1), LIGO Livingston Observatory (L1) and Virgo
Observatory (V1) around the time of the compact binary merger (CBC)
candidate S190828l (GCN Circular 25503
Loading...
 
 ). 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/S190828l

The preferred sky map at this time is LALInference.v2.fits.gz. The 90%
credible region is 359 deg2. Marginalized over the whole sky, the a
posteriori luminosity distance estimate is 1528 +/- 387 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)