GCN Circular 26916
Subject
LIGO/Virgo S200128d: Upper limits from Fermi-GBM Observations
Date
2020-01-28T14:21:50Z (5 years ago)
From
Joshua Wood at MSFC/Fermi-GBM <joshua.r.wood@nasa.gov>
J. Wood (NASA/MSFC) reports on behalf of the Fermi-GBM Team and the
GBM-LIGO/Virgo group
For S200128d and using the bayestar.fits.gz,1 skymap, Fermi-GBM was observing
48.7% 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 S200128d (GCN 26906). 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=266.6, Dec=-24.9 with a radius of 67.5 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: 2.5 3.2 8.3
1.024 s: 0.8 1.3 2.7
8.192 s: 0.2 0.4 1.0
Assuming the median luminosity distance of 4031 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: 7.8 8.5 37.
1.024s: 2.4 3.4 12.
8.192s: 0.7 1.0 4.5