GCN Circular 25522
Subject
LIGO/Virgo S190828j: Upper limits from Fermi-GBM Observations
Event
Date
2019-08-28T16:14:43Z (6 years ago)
From
Peter Veres at UAH <veresp@gmail.com>
P. Veres (UAH) reports on behalf of the Fermi-GBM Team and the
GBM-LIGO/Virgo group:
For S190828j and using the updated bayestar skymap (GCN 25504), Fermi-GBM
was observing 83% 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 S190828j (GCN 25497). 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 (in units of erg/s/cm^2):
Timescale Soft Normal Hard
--------------------------------------
0.128 s: 5.5e-07 7.5e-07 1.7e-06
1.024 s: 1.8e-07 2.8e-07 6.8e-07
8.192 s: 7.1e-08 1.3e-07 2.5e-07
Assuming the median luminosity distance of 1800 Mpc (z=0.34) from the GW
detection, we estimate the following intrinsic luminosity upper limits over
the 1 keV-10 MeV energy range (in units of 10^50 erg/s):
Timescale Soft Normal Hard
------------------------------------
0.128 s: 3.4 4.1 16
1.024 s: 1.1 1.5 6.2
8.192 s: 0.44 0.71 2.3