TITLE: GCN CIRCULAR NUMBER: 28469 SUBJECT: IceCube-200921A: Upper limits from Fermi-GBM Observations DATE: 20/09/22 02:48:51 GMT FROM: Rachel Hamburg at UAH R. Hamburg (UAH) reports on behalf of the Fermi-GBM team: For the IceCube high-energy neutrino candidate event IceCube-200921A (GCN 28468), at the event time Fermi-GBM was observing the reported neutrino location at: RA: 195.29 (+2.35 -1.73 deg 90% PSF containment) J2000 Dec: 26.24 (+1.51 -1.77 deg 90% PSF containment) J2000 There was no Fermi-GBM onboard trigger around the event time of the neutrino candidate. 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 the neutrino candidate time. From this search, no significant signal was found related to IceCube-200921A. We set upper limits on impulsive gamma-ray emission. 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^-6 erg/s/cm^2): Timescale Soft Normal Hard -------------------------------------- 0.128 s: 17. 34. 73. 1.024 s: 6.4 13. 21. 8.192 s: 2.2 2.5 1.4 These results are preliminary.