GCN Circular 27207

L. Scotton (CNRS/IN2P3/LUPM), M. Crnogorcevic (Univ. of Maryland & NASA/GSFC), N. Di Lalla (Stanford University), M. Axelsson (KTH & Stockholm Univ), E. Bissaldi (Politecnico & INFN Bari), D. Kocevski (NASA/MSFC), N. Omodei (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 
February 25, 2020, for possible high-energy (E > 100 MeV) gamma-ray emission in 
spatial/temporal coincidence with the LIGO/Virgo trigger S200225q (GCN 27193
Not found
 
 
).

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 ~3% of the LIGO probability at the time of the trigger
(T0 = 2020-02-25 06:04:21.397 UTC), and reached 100% cumulative coverage 
after ~5.3 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 1.8e-10 and 8.1e-7 [erg/cm^2/s].
  
The Fermi-LAT point of contact for this event is 
Lorenzo Scotton (lorenzo.scotton@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.