TITLE: GCN CIRCULAR NUMBER: 42365 SUBJECT: GRB 251016A: Fermi GBM Observation DATE: 25/10/18 23:23:26 GMT FROM: Jacob Smith at Fermi-GBM Team <jrs0118@uah.edu> Jacob Smith (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 14:59:19.76 UT on 16 October 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251016A (trigger 782319564/251016625), which is was detected by SVOM/ECLAIRs (Basa et al., GCN 42308), CALET-GBM (Kawakubo et al., GCN 42321), Glowbug (Woolf et al., GCN 42313) and Astro Sat CZTI (Arya et al., GCN 42327). The Fermi GBM on-ground location is consistent with the SVOM/ECLAIRs position. The angle from the Fermi LAT boresight is 42 degrees. The GBM light curve consists of a single emission episode with a duration (T90) of about 0.32 s (50-300 keV). The time-averaged spectrum from T0-0.1 to T0+0.4 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.83 +/- 0.04 and the cutoff energy, parameterized as Epeak, is 1317 +/- 145 keV. The event fluence (10-1000 keV) in this time interval is (3 +/- 0.08)E-06 erg/cm^2. The 64-ms peak photon flux measured starting from T0+0.13 s in the 10-1000 keV band is 34 +/- 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/42365. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...