TITLE: GCN CIRCULAR NUMBER: 34830 SUBJECT: GRB 231017A: Fermi GBM Detection DATE: 23/10/18 16:19:02 GMT FROM: Joe Mangan at IJCLab <joseph.mangan@ijclab.in2p3.fr> J.Mangan (CNRS/IJCLab), E. Bissaldi (Politecnico and INFN Bari) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 08:05:03.30 UT on 17 October 2023, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 231017A (trigger 719222708/231017337), which was also detected by the Swift/BAT-GUANO (DeLaunay et al. 2023, GCN 34824). The Fermi GBM Final Real-time Localization is reported in GCN 34822. The GBM light curve consists of a single emission episode with a duration (T90) of about 4.8 s (50-300 keV). The time-averaged spectrum from T0-3.5 to T0+4.7 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.1 +/- 0.2 and the cutoff energy, parameterized as Epeak, is 270 +/- 82 keV. A Band function fits the spectrum equally well with Epeak= 175 +/- 92 keV, alpha = -0.9 +/- 0.3 and beta = -1.9 +/- 0.3. The event fluence (10-1000 keV) in this time interval is (1.7 +/- 0.2)E-06 erg/cm^2. The 64-msec peak photon flux measured starting from T0+0.77 s in the 10-1000 keV band is 7.8 +/- 1.6 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/34830. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...