TITLE: GCN CIRCULAR NUMBER: 38757 SUBJECT: LIGO/Virgo/KAGRA S250101k: Upper limits from Fermi-GBM Observations DATE: 25/01/01 16:04:32 GMT FROM: Peter Veres at University of Alabama in Huntsville <veresp@gmail.com> P. Veres (UAH) reports on behalf of the Fermi-GBM Team: "For S250101k (GCN 38747) and using the initial bayestar skymap, Fermi-GBM was observing 100% 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 S250101k. 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. We set upper limits on impulsive gamma-ray emission for the complete GW localization region. 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: 1.4 2.4 4.9 1.024 s: 0.55 0.9 2.2 8.192 s: 0.14 0.23 0.59 Assuming the median luminosity distance of 3057 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: 2.5 3.7 12.0 1.024s: 0.98 1.4 5.7 8.192s: 0.25 0.36 1.5 View this GCN Circular online at https://gcn.nasa.gov/circulars/38757. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...