TITLE: GCN CIRCULAR NUMBER: 41852 SUBJECT: GRB 250917B: Fermi GBM Observation DATE: 25/09/17 18:53:07 GMT FROM: Rushikesh Digambar Sonawane PHD231014 at IISER, TVM <rushikesh23@iisertvm.ac.in> R. Sonawane (IISER, TVM) and C. Meegan (UAH) report on behalf ofthe Fermi Gamma-ray Burst Monitor Team:"At 06:27:44.33 UT on 17 September 2025, the Fermi Gamma-ray Burst Monitor (GBM)triggered and located GRB 250917B (trigger 779783269/250917269).which was also detected by Swift BAT (R. Caputo et al. 2025, GCN 41848).The Fermi GBM on-ground location is consistent with the Swift BAT position.The angle from the Fermi LAT boresight is 48 degrees.The GBM light curve consists of a single emission episode with a duration (T90)of about 0.2 s (50-300 keV). The time-averaged spectrumfrom T0-0.2 to T0+0.3 s is best fit bya power law function with an exponential high-energy cutoff.The power law index is -1 +/- 0.2 and the cutoff energy,parameterized as Epeak, is 120 +/- 20 keV.The event fluence (10-1000 keV) in this time interval is(3.2 +/- 0.3)E-07 erg/cm^2. The 64-ms peak photon flux measuredstarting from T0+0.0 s in the 10-1000 keV band is 24 +/- 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.htmlFor 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/41852. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...