TITLE: GCN CIRCULAR NUMBER: 42737 SUBJECT: GRB 251117A: Fermi GBM observation DATE: 25/11/18 15:50:37 GMT FROM: Elisabetta Bissaldi at Politecnico and INFN Bari <elisabetta.bissaldi@ba.infn.it> E. Bissaldi (Politecnico and INFN Bari) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 12:19:52.14 UT on 17 November 2025, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 251117A (trigger 785074797 / 251117514), which was also detected by the Fermi LAT (Holzmann Airasca et al., GCN 42729), SVOM/GRM (Wang et al., GCN 42731) and Swift/BAT-GUANO (DeLaunay et al. 2025, GCN 42732). The GBM on-ground location (GCN 42719) is consistent with the Fermi LAT position. The angle from the Fermi LAT boresight at the GBM trigger time is 50 degrees. The GBM light curve consists of a multi-peaked emission episode with a duration (T90) of about 1.3 s (50-300 keV). The time-averaged spectrum from T0-0.32 s to T0+1.15 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.80 +/- 0.08 and the cutoff energy, parameterized as Epeak, is 1.2 +/- 0.3 MeV. The event fluence (10-1000 keV) in this time interval is (2.04 +/- 0.08)E-06 erg/cm^2. The 64-ms peak photon flux measured starting from T0+0.32 s in the 10-1000 keV band is 11.1 +/- 1.1 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/42737. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...