[vsnet-grb-info 23023] LIGO/Virgo S190720a: Upper limits from Fermi-GBM Observations
GCN Circulars
gcncirc at capella2.gsfc.nasa.gov
Sat Jul 20 21:33:04 JST 2019
TITLE: GCN CIRCULAR
NUMBER: 25122
SUBJECT: LIGO/Virgo S190720a: Upper limits from Fermi-GBM Observations
DATE: 19/07/20 12:31:57 GMT
FROM: Joshua Wood at MSFC/Fermi-GBM <joshua.r.wood at nasa.gov>
J. Wood (NASA/MSFC) reports on behalf of the Fermi-GBM Team and the GBM-LIGO/Virgo group:
For the LIGO/Virgo detection of GW trigger S190720a (GCN 25115) and using the initial BAYESTAR skymap, Fermi-GBM was observing 73.2% of the localization probability at event time.
There was no Fermi-GBM onboard trigger around the event time of S190720a. 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 10^-8 erg/s/cm^2):
Timescale Soft Normal Hard
------------------------------------
0.128 s: 37. 57. 110.
1.024 s: 13. 17. 40.
8.192 s: 3.2 4.9 9.5
Assuming the median luminosity distance of 1071 Mpc (z=0.215) 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
------------------------------------
0.128 s: 78.6 110. 352.
1.024 s: 27.6 32.7 128.
8.192 s: 6.80 9.42 30.4
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