TITLE: GCN CIRCULAR NUMBER: 27209 SUBJECT: LIGO/Virgo S200225q: Upper limits from Fermi-GBM Observations DATE: 20/02/25 16:45:33 GMT FROM: Adam Goldstein at Fermi-GBM, USRA A. Goldstein (USRA) reports on behalf of the Fermi-GBM Team and the GBM-LIGO/Virgo group For S200225q and using the latest BAYESTAR skymap, Fermi-GBM was observing 88.6% 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 S200225q (GCN Circ. 27193). 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=224.3, Dec=24.7 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 Normal Hard --------------------------------- 0.128 s: 10. 13. 23. 1.024 s: 3.7 3.8 6.6 8.192 s: 0.9 1.0 2.0 Assuming the median luminosity distance of 1234 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: 2.8 3.3 9.8 1.024s: 1.0 1.0 2.8 8.192s: 0.2 0.2 0.8