GCN Circular 25610
Subject
LIGO/Virgo S190901ap: Upper limits from Fermi-GBM Observations
Date
2019-09-02T05:11:21Z (6 years ago)
From
C. Michelle Hui at MSFC/Fermi-GBM <c.m.hui@nasa.gov>
C. M. Hui (NASA/MSFC) reports on behalf of the Fermi-GBM Team and the GBM-LIGO/Virgo group
For S190901ap and using the initial bayestar skymap, Fermi-GBM was observing 61% 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 S190901ap (GCN 25606). 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.
Part of the LVC localization region is behind the Earth for Fermi, located at RA=112.4, Dec=-9.7 with a radius of 67.2 degrees. We therefore set upper limits on impulsive gamma-ray emission for the LVC localization region visible to Fermi at merger time. 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: 3.0 5.0 9.9
1.024 s: 0.9 1.5 3.5
8.192 s: 0.4 0.5 0.9
Assuming the median luminosity distance of 242 Mpc from the GW detection, we estimate the following intrinsic luminosity upper limits over the 1 keV-10 MeV energy range (in units of 10^48 erg/s):
Timescale Soft Normal Hard
------------------------------------
0.128 s: 3.2 5.0 16.2
1.024 s: 1.0 1.5 5.7
8.192 s: 0.4 0.5 1.5