TITLE: GCN CIRCULAR NUMBER: 17328 SUBJECT: GRB 150118C: Fermi GBM Detection DATE: 15/01/20 22:28:31 GMT FROM: Eric Burns at U of Alabama E. Burns (UAH) report on behalf of the Fermi GBM Team: "At 22:14:32.66 UT on 18 January 2015, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 150118C (trigger 443312075 / 150118927). The GBM on-ground location is consistent with the IPN location (K. Hurley et al. 2015, GCN 17324). The angle from the Fermi LAT boresight is 92 degrees. The GBM light curve consists of a single pulse with a duration (T90) of about 0.3 s (50-300 keV). The time-averaged spectrum from T0-0.128 s to T0+0.320 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.1 +/- 0.1 and the cutoff energy, parameterized as Epeak, is 658 +/- 143 keV. It is equally well fit by a Band function with Epeak = 415 +/- 117 keV, alpha = -0.9 +/- 0.1, and beta = -2.0 +/- 0.2. The event fluence (10-1000 keV) in this time interval is (1.2 +/- 0.1)E-06 erg/cm^2. The 64-ms peak photon flux measured starting from T0+0.00 s in the 10-1000 keV band is 39.6 +/- 2.0 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."