GCN Circular 35131
C. de Barra (UCD) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 17:16:29.83 UT on 18 November 2023, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 231118A (trigger 722020594 / 231118720), which was also detected by Swift BAT (S. Laha et al. 2023, GCN 35101) and Swift XRT (K.L. Page & P.A. Evens, 2023, GCN 35104). The Fermi Final Localization was reported in GCN 35100 and is consistent with the Swift BAT and XRT positions. The angle from the Fermi LAT boresight at the GBM trigger time is 118 degrees. The GBM light curve consists of a single peak with a duration (T90) of about 6 s (50-300 keV). The time-averaged spectrum from -4.1s to 6.1 s is best fit with a Band function with Epeak = 217.7 +/- 22.6 keV, alpha = -0.77 +/- 0.07, and beta = -2.17 +/- 0.13 The event fluence (10-1000 keV) in this time interval is (1.0 +/- 0.1)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+3.2 s in the 10-1000 keV band is 18.0 +/- 0.5 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/"