TITLE: GCN CIRCULAR NUMBER: 12221 SUBJECT: GRB 110731A: Fermi GBM observation DATE: 11/08/01 06:29:38 GMT FROM: David Gruber at MPE David Gruber (MPE) reports on behalf of the Fermi GBM Team: "At 11:09:29.94 UT on 31 July 2011, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 110731A (trigger 333803371 / 110731465) which which was also detected by Fermi LAT (Bregeon et al. 2011, GCN 12218) and Swift (Oates et al. 2011, GCN 12215). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight is 6 degrees. Moreover, this burst was bright enough to result in a Fermi spacecraft autonomous rapid repoint (ARR) maneuver. The GBM light curve consists of one pulse with a duration (T90) of about 7.3 +/- 0.3 s (50-300 keV). The time-averaged spectrum from T0 s to T0+7.3 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.82 +/- 0.03 and the cutoff energy, parameterized as Epeak, is 317 +/- 10 keV. The event fluence (10-1000 keV) in this time interval is (2.218 +/- 0.006)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.128 s in the 10-1000 keV band is 20.9 +/- 0.5 ph/s/cm^2. A Band function fits the spectrum equally well with Epeak= 304 +/- 13 keV, alpha = -0.80 +/- 0.03 and beta = -2.98 +/- 0.30. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."