GCN Circular 25021

M. Axelsson (KTH and Stockholm Univ.),
E. Bissaldi (Politecnico and INFN Bari) 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 July 6, 2019, for possible high-energy (E > 100 MeV) gamma-ray emission
in spatial/temporal coincidence with the LIGO/Virgo trigger S190706ai (GCN 24998
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 a time, and "cumulative coverage" as the integral
of the instantaneous coverage over time.
Fermi-LAT had instantaneous coverage of 45% of the LIGO probability
region at the time of the trigger (T0 = 2019-07-06 22:26:41.345 UTC),
and reached full coverage at T0+1 ks.

We performed a search for a transient counterpart
within the observed region of the 90% contour of the LIGO map
in a fixed time window from T0 to T0+10 ks.
No significant sources were 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 2e-10 and 5e-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.