TITLE: GCN CIRCULAR NUMBER: 26359 SUBJECT: LIGO/Virgo S191205ah: Upper limits from Fermi-GBM Observations DATE: 19/12/06 05:38:49 GMT FROM: Cori Fletcher at USRA C. Fletcher (USRA) reports on behalf of the Fermi-GBM Team and the GBM-LIGO/Virgo group For S191205ah and using the initial BAYESTAR skymap, Fermi-GBM was observing 93.7% 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 S191205ah (GCN Circ. 26350). 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=86.3, Dec=25.1 with a radius of 67.4 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: 5.0 9.4 26. 1.024 s: 1.7 3.4 7.2 8.192 s: 0.6 1.0 2.3 Assuming the median luminosity distance of 385 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 ------------------------------------ 0.128s: 14. 24. 83. 1.024s: 4.6 8.5 30. 8.192s: 1.5 2.5. 9.5