GCN Circular 27209
Subject
LIGO/Virgo S200225q: Upper limits from Fermi-GBM Observations
Date
2020-02-25T16:45:33Z (4 years ago)
From
Adam Goldstein at Fermi-GBM, USRA <adam.michael.goldstein@gmail.com>
A. Goldstein (USRA) reports on behalf of the Fermi-GBM Team and the
GBM-LIGO/Virgo group
For S200225q and using the latest BAYESTAR skymap, Fermi-GBM was observing
88.6% 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 S200225q (GCN Circ. 27193). 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=224.3, Dec=24.7 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: 10. 13. 23.
1.024 s: 3.7 3.8 6.6
8.192 s: 0.9 1.0 2.0
Assuming the median luminosity distance of 1234 Mpc from the GW detection,
we estimate the following intrinsic luminosity upper limits over the 1
keV-10 MeV energy range (in units of 10^50 erg/s):
Timescale Soft Normal Hard
------------------------------------
0.128s: 2.8 3.3 9.8
1.024s: 1.0 1.0 2.8
8.192s: 0.2 0.2 0.8