GCN Circular 18220
P. Veres (UAH) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 22:19:27.158 UT on 31 August 2015, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 150831B (trigger 462752371 / 150831930) which was also detected by the Swift/BAT and XRT (Marshall et al. 2015, GCN 18215 and Evans et al. 2015, GCN 18217) The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 96 degrees. The GBM light curve has a duration (T90) of about 13.8 s (50-300 keV). The time-averaged spectrum from T0-4.0 s to T0+6.3 s is adequately fit by a power law function with an exponential high-energy cutoff. The power law index is -0.93 +/- 0.12 and the cutoff energy, parameterized as Epeak, is 82.3 +/- 5.5 keV. The event fluence (10-1000 keV) in this time interval is (2.51 +/- 0.11)E-6 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.1 s in the 10-1000 keV band is 9.1 +/- 0.4 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."