[vsnet-grb-info 23796] LIGO/Virgo S190930s: No counterpart candidates in Fermi-LAT observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  25895
SUBJECT: LIGO/Virgo S190930s: No counterpart candidates in Fermi-LAT observations
DATE:    19/10/01 09:59:05 GMT
FROM:    Magnus Axelsson at Stockholm U.  <magaxe at kth.se>

M. Kovacevic (INFN Perugia), L. Scotton (Univ. and INFN, Torino), M. Axelsson (KTH and Stockholm Univ.), F. Longo (Univ. and INFN Trieste), E. Bissaldi (Politecnico and INFN Bari), N. Omodei (Stanford Univ.), M. Arimoto (Kanazawa Univ.) 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 Sep 30, 2019, for possible high-energy (E > 100 MeV) gamma-ray emission in spatial/temporal coincidence with the LIGO/Virgo trigger S190930s (GCN 25871).

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 null instantaneous coverage of the LIGO probability region at the time of the trigger (T0 = 2019-09-30 13:35:41.247 UTC). Coverage started around 300 s after the trigger and reached 99% cumulative coverage at approximately T0 + 4 ks. The remaining area was not observed within 10 ks after the trigger.

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 between 100 MeV and 1 GeV for the fixed time interval of this search vary between 1.4e-10 and 8.1e-08 [erg/cm^2/s].

The Fermi-LAT point of contact for this event is Nicola Omodei (nikomo at stanford.edu<mailto:nikomo at stanford.edu>).

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.