GCN Circular 25887
Subject
LIGO/Virgo S190930t: Upper limits from Fermi-GBM Observations
Date
2019-09-30T20:01:02Z (5 years ago)
From
Joshua Wood at MSFC/Fermi-GBM <joshua.r.wood@nasa.gov>
J. Wood (NASA/MSFC) reports on behalf of the Fermi-GBM Team and the GBM-LIGO/Virgo group
For S190930t and using the initial bayestar.fits.gz skymap, Fermi-GBM was observing 58.5% of the localization probability at event time.
There was no Fermi-GBM onboard trigger around the event time of the LIGO/Virgo detection of GW trigger S190930t (GCN 25876). An automated, blind search for short gamma-ray bursts below the onboard triggering threshold in Fermi-GBM also identified no counterpart candidates. The GBM targeted search, the most sensitive, coherent search for GRB-like signals, was run from +/-30 s around merger time, and also identified no counterpart candidates.
We therefore set upper limits on impulsive gamma-ray emission. Using the representative soft, normal, and hard GRB-like templates described in arXiv:1612.02395, we set the following 3 sigma flux upper limits over 10-1000 keV, weighted by GW localization probability (in units of 10^-7 erg/s/cm^2):
Timescale Soft Normal Hard
------------------------------------
0.128 s: 2.8 4.1 8.8
1.024 s: 0.8 1.2 2.6
8.192 s: 0.3 0.4 0.8
Assuming the median luminosity distance of 108 Mpc from the GW detection, we estimate the following intrinsic luminosity upper limits over the 1 keV-10 MeV energy range (in units of 10^47 erg/s):
Timescale Soft Normal Hard
------------------------------------
0.128 s: 5.93 8.13 28.7
1.024 s: 1.61 2.38 8.47
8.192 s: 0.64 0.83 2.57