C.M. Hui and C. A. Wilson-Hodge (NASA/MSFC) reports on behalf of the Fermi-GBM Team and the GBM-LIGO/Virgo group
For S190503bf and using the initial BAYESTAR skymap, Fermi-GBM was observing 62% 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 S190503bf (GCN 24377). 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=73.8, Dec=21.9 with a radius of 67.2 degrees. We therefore set upper limits on impulsive gamma-ray emission considering the 90% credible region of the GW localization not blocked by the Earth. 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^-7 erg/s/cm^2):
Timescale Soft Normal Hard
0.1 s: 4.1-4.6 8.6-9.5 27.-28.
1.0 s: 1.2-1.4 2.7-2.9 7.9-8.3
10 s: 0.3-0.4 0.8-0.9 2.5-2.6
Assuming the median luminosity distance of ~421 Mpc from the GW detection, we estimate intrinsic luminosity upper limits of (0.1-1.5) E49 erg/s for the soft template, (0.2-2.8)E49 erg/s for the normal template, and (1.2-14.)E49 erg/s for the hard template over the 1 keV-10 MeV energy range.