[vsnet-grb-info 24264] LIGO/Virgo S191205ah: No counterpart candidates in Fermi-LAT observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  26363
SUBJECT: LIGO/Virgo S191205ah: No counterpart candidates in Fermi-LAT observations
DATE:    19/12/06 13:04:09 GMT
FROM:    Lorenzo Scotton at CNRS/IN2P3/LUPM  <lorenzoscotton at live.it>

L. Scotton (CNRS/IN2P3/LUPM), M. Axelsson (KTH & Stockholm Univ.), E. Bissaldi (Politecnico & INFN Bari)

D. Kocevski (NASA/MSFC), N. Omodei (Stanford Univ.), F.Longo (University and INFN, Trieste) and

M. Arimoto (Kanazawa Univ.)

report on behalf of the Fermi-LAT Collaboration:

We have searched data collected by the Fermi Large Area Telescope (LAT) on
December 5th, 2019, for possible high-energy (E > 100 MeV) gamma-ray emission in
spatial/temporal coincidence with the LIGO/Virgo trigger S191205ah (GCN 26350).

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 ~10% of the LIGO probability at the time of the trigger
(T0 = 2019-12-05 21:52:08 UTC), and reached 100% cumulative coverage
after ~6.2 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.

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 4e-11 and 2e-07 [erg/cm^2/s].

The Fermi-LAT point of contact for this event is
Lorenzo Scotton (lorenzo.scotton at lupm.in2p3.fr<mailto:lorenzo.scotton at lupm.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.