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GCN Circular 27286

LIGO/Virgo S200302c: Upper limits from Fermi-GBM Observations
2020-03-02T15:25:48Z (4 years ago)
Colleen A. Wilson at NASA/MSFC/NSSTC <>
For S200302c and using the initial bayestar.fits.gz skymap, Fermi-GBM was observing 71.1% 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 S200302c (GCN 27278). 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=288.0, Dec=1.6 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: 3.9        6.1      12
1.024 s: 1.4        2.0      3.7
8.192 s: 0.40       0.73     1.8

Assuming the median luminosity distance of 1737.4 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
0.128 s:   2.2      3.1     10
1.024 s:   0.79     1.0     3.1
8.192 s:   0.23     0.37    1.5
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