GCN Circular 25699
Subject
LIGO/Virgo S190910d: Upper limits from Fermi-GBM Observations
Date
2019-09-10T06:18:11Z (6 years ago)
From
Cori Fletcher at USRA <cfletcher@usra.edu>
C. Fletcher (USRA) reports on behalf of the Fermi-GBM Team and the GBM-LIGO/Virgo group
For S190910d and using the initial bayestar skymap, Fermi-GBM was observing 91.6% 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 S190910d (GCN 25695). 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=194.6, Dec=-9.9 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 norm hard
--------------------------------------
0.128 s: 3.3 6.5 12
1.024 s: 1.0 1.8 4.6
8.192 s: 0.4 0.67 1.3
Assuming the median luminosity distance of 606 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: 22 40 122
1.024 s: 6.7 11 47
8.192 s: 2.7 4.1 13