TITLE: GCN CIRCULAR NUMBER: 42047 SUBJECT: GRB 251001B: Fermi GBM Observation DATE: 25/10/01 21:33:18 GMT FROM: eliza.neights@gmail.com Eliza Neights (GWU, NASA GSFC) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 14:17:19.05 UT on 01 October 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251001B (trigger 781021044/251001595) which was also detected by Swift BAT (A. P. Beardmore et al. 2025, GCN 42039). The Fermi GBM on-ground location is consistent with the Swift BAT position. The angle from the Fermi LAT boresight is 53 degrees. The GBM light curve consists of a single emission episode with a duration (T90) of about 19 s (50-300 keV). The time-averaged spectrum from T0-3.7 to T0+16.7 s is best fit by a Comptonized function with index 0.22 +/- 0.03 and peak energy 107 +/- 5 keV. The event fluence (10-1000 keV) in this time interval is (1.3 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.7 s in the 10-1000 keV band is 1.4 +/- 0.2 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/42047. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...