GCN Circular 24115

E. Bissaldi (INFN & Politecnico Bari), M. Axelsson (KTH & Stockholm Univ.)
and N. Omodei (Stanford Univ.) report on behalf of the Fermi-LAT Collaboration:


We have searched data collected by the Fermi Large Area Telescope (LAT) on
April 12, 2019, for possible high-energy (E>100 MeV) gamma-ray emission in
spatial/temporal coincidence with the LIGO/Virgo trigger S190412m.

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 ~99% of the LIGO probability at the time of the trigger
(T0 = 2019-04-12 05:30:44 UTC), and reached 100% cumulative coverage
after ~7 ks.

We performed a search for a transient counterpart within the 90% contour of
the 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. Again, no significant candidate
counterpart was found.

Energy flux upper bounds for the fixed time interval between 100 MeV and 100 GeV
for this search vary between 2e-10 and 3e-09 [erg/cm^2/s].

The Fermi-LAT point of contact for this event is
Elisabetta Bissaldi (Elisabetta.Bissaldi@ba.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.