GCN Circular 25823
Subject
LIGO/Virgo S190923y: Upper limits from Fermi-GBM Observations
Event
Date
2019-09-23T19:16:28Z (6 years ago)
From
Bagrat Mailyan at UAH <bm0054@uah.edu>
B. Mailyan (UAH) and J. Wood (NASA) report on behalf of the Fermi-GBM Team
and the GBM-LIGO/Virgo group
For S190923y and using the initial bayestar skymap, Fermi-GBM was observing
42.3% 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 S190923y (GCN 25814).
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 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: 2.2 4.1 8.8
1.024 s: 0.74 1.3 2.4
8.192 s: 0.26 0.4 0.79
Assuming the median luminosity distance of 438 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
------------------------------------
0.128s: 9.4 16.2 57.4
1.024s: 3.2 5.1 15.6
8.192s: 1.1 1.6 5.2