LIGO/Virgo S200311bg

The LIGO Scientific Collaboration and the Virgo Collaboration report:

We identified the compact binary merger candidate S200311bg during
real-time processing of data from LIGO Hanford Observatory (H1), LIGO
Livingston Observatory (L1), and Virgo Observatory (V1) at 2020-03-11
11:58:53.398 UTC (GPS time: 1267963151.398). The candidate was found
by the GstLAL [1], CWB [2], PyCBC Live [3], SPIIR [4], and MBTAOnline
[5] analysis pipelines.

S200311bg is an event of interest because its false alarm rate, as
estimated by the online analysis, is 8.9e-26 Hz, or about one in 1e18
years. The event's properties can be found at this URL:
https://gracedb.ligo.org/superevents/S200311bg

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, the probability
that the lighter compact object has a mass < 3 solar masses (HasNS) is
<1%. Using the masses and spins inferred from the signal, the
probability of matter outside the final compact object (HasRemnant) is
<1%.

Two sky maps are available at this time and can be retrieved from the
GraceDB event page:
 * bayestar.fits.gz,0, an initial localization generated by BAYESTAR
[6], distributed via GCN notice about 2 minutes after the candidate
event time.
 * bayestar.fits.gz,1, an initial localization generated by BAYESTAR
[6], distributed via GCN notice about 10 minutes after the candidate
event time.

The preferred sky map at this time is bayestar.fits.gz,1. For the
bayestar.fits.gz,1 sky map, the 90% credible region is well fit by an
ellipse with an area of 52 deg2 described by the following DS9 region
(right ascension, declination, semi-major axis, semi-minor axis,
position angle of the semi-minor axis):
   icrs; ellipse(00h08m, -07d27m, 8.54d, 1.98d, 72.86d)
Marginalized over the whole sky, the a posteriori luminosity distance
estimate is 924 +/- 188 Mpc (a posteriori mean +/- standard
deviation).

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

 [1] Messick et al. PRD 95, 042001 (2017)
 [2] Klimenko et al. PRD 93, 042004 (2016)
 [3] Nitz et al. PRD 98, 024050 (2018)
 [4] Qi Chu, PhD Thesis, The University of Western Australia (2017)
 [5] Adams et al. CQG 33, 175012 (2016)
 [6] Singer & Price PRD 93, 024013 (2016)

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
S200311bg
 in a time range of 1000 seconds [3] centered on the alert event time
(2020-03-11 11:50:33.398 UTC to 2020-03-11 12:07:13.398 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
S200311bg calculated from the map circulated in the 2-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 S200311bg ranges from 0.029 to 0.194 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] PoS(ICRC2019)918 and Braun et al., Astroparticle Physics 29, 299 (2008)
[3] Baret et al., Astroparticle Physics 35, 1 (2011)

C. Ferrigno, V. Savchenko (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 S200311bg (GCN 27358
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 ).

At the time of the event (2020-03-11 11:58:53 UTC, hereafter T0),
INTEGRAL was operating in nominal mode. The peak of the event
localization probability was at an angle of 90 deg with respect to the
spacecraft pointing axis, near the direction of the Sun.
This orientation implies strongly suppressed (6% of optimal) response of 
ISGRI,
strongly suppressed (29% of optimal) response of IBIS/Veto,
and strongly suppressed (34% 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 4.5e-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 ~4.7e-07 (1.4e-07)
erg/cm^2/s at 1 s (8 s) time scale in 75-2000 keV energy range.

For the mean reported distance 924.0 Mpc this corresponds to the limit
on the total isotropic equivalent energy in 1 s of 4.6e+49 erg for
the short GRB spectrum and for a long GRB spectrum isotropic
equivalent luminosity in 1 s (8 s) of 4e+49 erg/s (1.5e+49 erg/s)

We report for completeness and in order of FAP, all excesses
identified in the search region. We find: 5 likely background
excesses:

T-T0 | scale | S/N | luminosity ( x 1e+49 erg/s) | FAP
5.44 | 0.45 | 3.2 | 7.71 +/- 2.48 +/- 2.65 | 0.161
134 | 2.25 | 3.6 | 3.71 +/- 1.1 +/- 1.28 | 0.382
28.8 | 1 | 3 | 4.72 +/- 1.66 +/- 1.62 | 0.633
159 | 2.1 | 3.4 | 3.74 +/- 1.14 +/- 1.28 | 0.7
110 | 0.45 | 3.9 | 9.35 +/- 2.48 +/- 3.21 | 0.875

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 result s 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

F. Longo (Univ. Trieste, and INFN Trieste)  M. Pilia (INAF/OA-Cagliari),
M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), C.Casentini,
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) report on behalf of the
AGILE Team:

In response to the LIGO/Virgo GW event S200311bg at T0 = 2020-03-11
11:58:53.398 (UTC), a preliminary analysis of the AGILE MCAL
and GRID data found no acquisitions around T0, due to a complete
Earth occultation of the S200311bg 90% c.l. localization region.

Additional analysis of AGILE data is in progress.

S. Sugita, M. Serino (AGU),
N. Kawai (Tokyo Tech), H. Negoro (Nihon U.),
M. Nakajima, W. Maruyama, M. Aoki, K. Kobayashi, R. Takagi (Nihon U.),
T. Mihara, C. Guo, Y. Zhou, 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, 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), M.
Sugizaki (NAOC)
report on behalf of the MAXI team:

We examined MAXI/GSC all-sky X-ray images (2-20 keV)
after the LVC trigger S200311bg at 2020-03-11 11:58:53.398 UTC (GCN 27358
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 ).

At the trigger time of S200311bg, the high-voltage of MAXI/GSC was off,
and it was turned on at T0+1163 sec (+19.4 min).
The first one-orbit (92 min) scan observation with GSC after the event
covered 81%
of the 90% credible region of the bayestar skymap from 12:18:16 to
12:20:08 UTC (T0+1163 to T0+1275 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.

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



At the time of S200311bg, Fermi was passing through the South Atlantic Anomaly from 2.9 minutes prior to 24.6 minutes after the trigger time; therefore the GBM detectors were disabled.

M. Kovacevic (INFN Perugia), M. Ohno (Hiroshima University), M. Axelsson
(KTH & Stockholm Univ),
E. Bissaldi (Politecnico & INFN Bari), D. Kocevski (NASA/MSFC), N. Omodei
(Stanford Univ.), N. Di Lalla (Stanford Univ.) 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
March 11, 2020, for possible high-energy (E > 100 MeV) gamma-ray emission
in
spatial/temporal coincidence with the LIGO/Virgo trigger S200311bg (GCN
27358
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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 time,
and "cumulative
coverage" as the integral of the instantaneous coverage over time.

The Fermi Gamma-ray Space Telescope was passing through the South Atlantic
Anomaly (SAA)
at the time of the trigger (T0 = 2020-03-11 11:58:53.398 UTC). During SAA
passages both the LAT
and the Gamma-ray Burst Monitor (GBM) do not collect data due to the high
charged particle
background in this region.

The LAT resumed taking data upon exiting the SAA at roughly T0 + 1.6 ks.

At that time the instantaneous coverage was 100% of the LIGO probability
map, therefore
100% cumulative coverage was reached at that time as well.

We performed a search for a transient counterpart within the observed
region of
the 90% contour of LIGO map in  a fixed time window from T0 + 1.6 ks to T0
+ 10 ks.
No significant new sources are 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 8.0e-10 and 1.1e-8 [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-ASDC), S. Emery (UCL-MSSL),
P. A. Evans (U. Leicester), P. Giommi (ASI), C. Gronwall (PSU),
D. Hartmann (Clemson U.), J. A. Kennea (PSU),
N. Klingler (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 (U. of Birmingham), 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 (U. Toronto),
E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift team:

Around the trigger time (T0) of LIGO/Virgo S200311bg
(LIGO/VIRGO Collaboration GCN Circ. 27358
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 ),
Swift/BAT was in the South Atlantic Anomaly (SAA)
until T0+60 s. Therefore, no science data
were collected during this time.

The results of the BAT analysis are available at
https://swift.gsfc.nasa.gov/results/BATbursts/team_web/S200311bg/web/source_public.html

S. Torii (Waseda U), A. Yoshida, T. Sakamoto, V. Pal'shin, 
S. Sugita (AGU), Y. Kawakubo (LSU), K. Yamaoka (Nagoya U),
S. Nakahira (RIKEN), Y. Asaoka (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 S200311bg,
T0 = 2020-03-11 11:58:53.398 UT (The LIGO Scientific Collaboration 
and Virgo Collaboration, GCN Circ. 27358
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 ), the CALET Gamma-ray 
Burst Monitor (CGBM) high voltages were off (from T0-3 min to 
T0+15 min).

The CALET Calorimeter (CAL) was operating in the high energy trigger
mode at the trigger time of S200311bg. 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. There
was no significant overlap with the LVC high probability localization 
region at T0+-60 sec.  The CAL FOV was centered at RA = 191.3 deg, 
Dec = +51.5 deg at T0.

The LIGO Scientific Collaboration and the Virgo Collaboration report:

We have conducted further analysis of the LIGO Hanford Observatory
(H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1)
data around the time of the compact binary merger (CBC) candidate
S200311bg (GCN Circular 27358
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 ).
Parameter estimation has been performed using LALInference [1] and a
new sky map, LALInference.fits.gz,0, distributed via GCN Notice, is
available for retrieval from the GraceDB event page:

https://gracedb.ligo.org/superevents/S200311bg

The preferred sky map at this time is LALInference.fits.gz,0. For the
LALInference.fits.gz,0 sky map, the 90% credible region is well fit by
an ellipse with an area of 34 deg2 described by the following DS9
region (right ascension, declination, semi-major axis, semi-minor
axis, position angle of the semi-minor axis):
   icrs; ellipse(00h09m, -08d14m, 6.91d, 1.59d, 72.77d)
Marginalized over the whole sky, the a posteriori luminosity distance
estimate is 1115 +/- 175 Mpc (a posteriori mean +/- standard
deviation).

Based on posterior support from parameter estimation [1], under the
assumption that the candidate S200311bg is astrophysical in origin,
the probability that the lighter compact object has a mass < 3 solar
masses (HasNS) is <1%. Using the masses and spins inferred from the
signal, the probability of matter outside the final compact object
(HasRemnant) is <1%.

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)

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

Konus-Wind (KW) was observing the whole sky at the time of the
LIGO/Virgo event S200311bg (2020-03-11 11:58:53.398 UTC, hereafter T0;
LIGO/Virgo Collaboration GCN Circ. 27358
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 ).

No triggered KW GRBs happened between ~3 hours before and ~1.5 days
after T0. Using waiting-mode data within the interval T0 +/- 100 s,
we found no significant (> 5 sigma) excess over the background
in both KW detectors on temporal scales from 2.944 s to 100 s.

We estimate an upper limit (90% conf.) on the 20 - 1500 keV fluence
to 8.2x10^-7 erg/cm^2 for a burst lasting less than 2.944 s and having a
typical KW short GRB spectrum (an exponentially cut off power law with
alpha =-0.5 and Ep=500 keV). For a typical long GRB spectrum (the Band
function with alpha=-1, beta=-2.5, and Ep=300 keV), the corresponding
limiting peak flux is 2.4x10^-7 erg/cm^2/s (20 - 1500 keV, 2.944 s scale).

All the quoted values are preliminary.