[vsnet-grb-info 25191] LIGO/Virgo S200302c: No significant counterpart candidates in Fermi-LAT observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  27291
SUBJECT: LIGO/Virgo S200302c: No significant counterpart candidates in Fermi-LAT observations
DATE:    20/03/03 01:38:51 GMT
FROM:    Makoto Arimoto at Tokyo Inst of Tech  <arimoto at hp.phys.titech.ac.jp>

N. Di Lalla (Stanford Univ.), F. Longo (University and INFN, Trieste),
D. Kocevski (NASA/MSFC),
N. Omodei (Stanford Univ.), M. Arimoto (Kanazawa Univ.), A. Berretta
(University & INFN Perugia),
M. Crnogorcevic (Univ. of Maryland & NASA/GSFC), M. Axelsson (KTH &
Stockholm Univ) and
E. Bissaldi (Politecnico & INFN Bari) report on behalf of the
Fermi-LAT Collaboration:

We have searched data collected by the Fermi Large Area Telescope (LAT) on
March 2, 2020, for possible high-energy (E > 100 MeV) gamma-ray emission in
spatial/temporal coincidence with the LIGO/Virgo trigger S200302c (GCN 27278).

We define "instantaneous coverage" as the integral over the region of the LIGO
probability map that is within the LAT field of view at a given time,
and "cumulative
coverage" as the integral of the instantaneous coverage over time. Fermi-LAT had
an instantaneous coverage of ~23% of the LIGO probability at the time
of the trigger
(T0 = 2020-03-02 01:58:11.519 UTC), and reached 100% cumulative coverage
after ~5 ks.

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 to T0 + 10 ks.
No significant new sources are found.

A marginally significant excess (with a  soft spectrum) was found at
the location
RA, Dec  63.3, Dec = 18.8 (degrees, J2000)
with an error radius of 1.0 deg (90% containment, statistical error only).

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 1.1e-10 and 1.1e-09 [erg/cm^2/s].

The Fermi-LAT point of contact for this event is
Makoto Arimoto (arimoto at se.kanazawa-u.ac.jp).

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.