TITLE: GCN CIRCULAR NUMBER: 13553 SUBJECT: GRB 120728B: Fermi GBM detection DATE: 12/07/31 20:59:26 GMT FROM: Suzanne Foley at MPE S. Foley (UCD/MPE) reports on behalf of the Fermi GBM Team: "At 10:25:24.24 UT on 28 July 2012, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 120728B (trigger 365163927 / 120728434) which was also detected by Konus-Wind (Golenetskii et al., GCN 13552). This burst was localized by the IPN (Hurley et al., GCN 13549). The GBM on-ground calculated location is consistent with the IPN location. The angle from the Fermi LAT boresight is 117 degrees. Moreover, this burst was bright enough to result in a Fermi spacecraft autonomous repoint request (ARR) maneuver. The GBM light curve consists of multiple pulses with a duration (T90) of about 105 s (50-300 keV). The time-averaged spectrum from T0+8.7 s to T0+113.2 s is well fit by a power law function with an exponential high-energy cutoff. The power law index is -1.31 +/-0.01 and the cutoff energy, parameterized as Epeak, is 94.86 (+1.04/-1.01) keV. The event fluence (10-1000 keV) in this time interval is (1.27 +/- 0.02)E-4 erg/cm^2. The 1-sec peak photon flux measured starting from T0+69.6 s in the 10-1000 keV band is 42.8 +/- 0.6 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."