GCN Circular 26118
B. Mailyan (UAH) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 21:23:31.13 UT on 31 October 2019, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 191031D (trigger 594249816/191031891) which was also detected by the Swift BAT and XRT (D'Elia et al. 2019, GCN 26112) The Fermi GBM Final Real-time Localization (GCN 26111) is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 64 degrees. The GBM light curve shows a short spike with a duration (T90) of about 0.256 s (50-300 keV). The time-averaged spectrum from T0-0.064 s to T0+0.32 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.42 +/- 0.04 and the cutoff energy, parameterized as Epeak, is 856 +/- 53 keV The event fluence (10-1000 keV) in this time interval is (4.36 +/- 0.09)E-06 erg/cm^2. The 64 ms peak photon flux measured starting from T0+0.128 s in the 10-1000 keV band is 48.7 +/- 1.59 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/"