TITLE: GCN CIRCULAR NUMBER: 43120 SUBJECT: GRB 251214B: Fermi GBM Observation DATE: 25/12/15 13:26:50 GMT FROM: Marianna Dafčíková at Masaryk University <500025@mail.muni.cz> M. Dafcikova (MUNI) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 09:02:18.03 UT on 14 December 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251214B (trigger 787395743/251214377), which was also detected by Swift BAT (R. A. J. Eyles-Ferris et al. 2025, GCN 43089) and GECAM-B (X. H. Luo et al. 2025, GCN 43113). The Fermi GBM on-ground location is consistent with the Swift BAT position. The angle from the Fermi LAT boresight is 97 degrees. The GBM light curve consists of a double-peaked emission with a duration (T90) of about 15 s (50-300 keV). The time-averaged spectrum from T0-0.6 to T0+9.9 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.81 +/- 0.05 and the cutoff energy, parameterized as Epeak, is 1280 +/- 80 keV. The event fluence (10-1000 keV) in this time interval is (1.3 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0-0.58 s in the 10-1000 keV band is 3.3 +/- 0.3 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/43120. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...