TITLE: GCN CIRCULAR NUMBER: 25714 SUBJECT: LIGO/Virgo S190910h: Upper limits from Fermi-GBM Observations DATE: 19/09/10 12:40:57 GMT FROM: Cori Fletcher at USRA C. Fletcher (USRA) reports on behalf of the Fermi-GBM Team and the GBM-LIGO/Virgo group For S190910h and using the initial bayestar skymap, Fermi-GBM was observing 59.9% 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 S190910h (GCN 25707). 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=357.1, Dec=16.0 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 norm hard -------------------------------------- 0.128 s: 3.3 5.7 12 1.024 s: 0.99 1.5 3.2 8.192 s: 0.32 0.53 0.93 Assuming the median luminosity distance of 242 Mpc from the GW detection, we estimate the following intrinsic luminosity upper limits over the 1 keV-10 MeV energy range (in units of 10^48 erg/s): Timescale Soft Normal Hard ------------------------------------ 0.128 s: 3.5 5.7 19.7 1.024 s: 1.1 1.5 5.2 8.192 s: 0.34 0.53 1.5