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GCN Circular 24583

LIGO/Virgo S190517h: Fermi-LAT search for a high-energy gamma-ray counterpart
2019-05-17T17:27:30Z (5 years ago)
Francesco Longo at U of Trieste,INFN Trieste <>
M. Axelsson (KTH and Stockholm Univ.), F. Longo (Univ. and INFN Trieste),
N. Omodei (Stanford) and D. Kocevski (NASA/MSFC) report on behalf of the
Fermi-LAT Collaboration:

We have searched data collected by the Fermi Large Area Telescope (LAT) on
May 17, 2019, for possible high-energy (E > 100 MeV) gamma-ray emission in
spatial/temporal coincidence with the LIGO/Virgo trigger S190517h (GCN

We define "instantaneous coverage" as the integral over the region of the
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 ~35% of the LIGO probability
at the time of the trigger (T0 = 2019-05-17 05:51:01.83 UTC), and reached
100% cumulative coverage after ~7.1ks.

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
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

Energy flux upper bounds for the fixed time interval between 100 MeV and 1
for this search vary between 1.7e-10 and 4.0e-09 [erg/cm^2/s].

The Fermi-LAT point of contact for this event is Magnus Axelsson (

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.
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