TITLE: GCN CIRCULAR NUMBER: 42037 SUBJECT: GRB 251001A: Fermi GBM Detection DATE: 25/10/01 14:15:23 GMT FROM: Marianna Dafčíková at Masaryk University <500025@mail.muni.cz> M. Dafcikova (MUNI), S. Lesage (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 02:40:56.95 UT on 01 October 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251001A (trigger 780979261/251001112). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 224.44, Dec = -56.23 (J2000 degrees, equivalent to J2000 14h 57m, -56d 13'), with a statistical uncertainty of 1.79 degrees. (radius, 1-sigma containment, statistical only; there is additionally a systematic error which we have characterized as a mixture of two Gaussians, one with a radius of 1.8 degrees (52% contribution) and one with a radius of 4.1 degrees (47% contribution) [A. Goldstein et al. 2020, ApJ, 895, 1]). The angle from the Fermi LAT boresight is 116 degrees. The GBM light curve consists of two peaks with a duration (T90) of about 7 s (50-300 keV). The time-averaged spectrum from T0+0.003 to T0+8.640 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.63 +/- 0.08 and the cutoff energy, parameterized as Epeak, is 138 +/- 7 keV. The event fluence (10-1000 keV) in this time interval is (4.4 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+6.0 s in the 10-1000 keV band is 24.8 +/- 0.6 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/42037. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...