TITLE: GCN CIRCULAR NUMBER: 18358 SUBJECT: GRB 150922A: Fermi GBM observation DATE: 15/09/23 09:04:05 GMT FROM: Oliver Roberts at UCD/Fermi O.J. Roberts (UCD), A. von Kienlin (MPE) and C. Meegan (UAH),report on behalf of the Fermi GBM Team: "At 05:37:29.08 UT on 22 September 2015, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 150922A (trigger 464593053 / 150922234), which was also detected by IPN (Svinkin et al. 2015, GCN 18357). The GBM on-ground location is consistent with the IPN position. The angle from the Fermi LAT boresight is about 38 degrees. The GBM light curve shows a short burst with a duration (T90) of 0.144 s (50-300 keV). The time-averaged spectrum from T0-0.016 to T0+0.128 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.55 +/- 0.11 and the cutoff energy, parameterized as Epeak, is 625 +/- 97 keV. The event fluence (10-1000 keV) in this time interval is (8.0 +/- 0.4) E-07 erg/cm^2. The 64 ms peak photon flux measured starting from T0-0.016 s in the 10-1000 keV band is 23.0 +/- 1.3 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."