TITLE: GCN CIRCULAR NUMBER: 38231 SUBJECT: LIGO/Virgo/KAGRA S241114bi: Upper limits from Fermi-GBM Observations DATE: 24/11/15 05:13:30 GMT FROM: Sarah Dalessi at UAH sd0104@uah.edu
S. Dalessi (UAH) reports on behalf of the Fermi-GBM Team:
For S241114bi (GCN 38228) and using the initial bayestar skymap, Fermi-GBM was observing 59.4% of the localization probability at event time.
There was no Fermi-GBM onboard trigger around the event time of the LIGO/Virgo/KAGRA (LVK) detection of GW trigger S241114bi. 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 LVK localization region is behind the Earth for Fermi, located at an RA=63.3, Dec=4.0 with a radius of 68.0 degrees. We therefore set upper limits on impulsive gamma-ray emission for the GW 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: 1.2 2.0 3.7 1.024 s: 0.42 0.66 1.2 8.192 s: 0.13 0.18 0.22
Assuming the median luminosity distance of 781.7 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: 0.14 0.21 0.63 1.024s: 0.047 0.068 0.20 8.192s: 0.015 0.019 0.038
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