TITLE: GCN CIRCULAR NUMBER: 15554 SUBJECT: GRB 131128A; Fermi GBM observation DATE: 13/11/29 20:02:16 GMT FROM: Hoi-Fung Yu at MPE Subject: GRB 131128A: Fermi GBM observation Hoi-Fung Yu (MPE) reports on behalf of the Fermi GBM Team: "At 15:06:25.28 UT on 28 November 2013, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 131128A (trigger 407343988 / 131128629), which was also detected by the Swift/BAT (Sonbas et al., GCN 15533). This burst, tentatively classified as a particle event by the FSW onboard, is in fact a gamma-ray burst. The GBM on-ground location is consistent with the Swift/XRT position. The angle from the Fermi LAT boresight is 71 degrees. The GBM light curve consists of a single pulse with a duration (T90) of ~2.0 s (50-300 keV). The time-averaged spectrum from T0-1.024 s to T0+2.560 s is adequately fit by a power law function with an exponential high-energy cutoff. The power law index is -0.9 +/- 0.3 and the cutoff energy, parameterized as Epeak, is 61.0 +/- 9.0 keV. The event fluence (10-1000 keV) in this time interval is (4.4 +/- 0.5)E-07 erg/cm^2. The 1-sec peak photon flux measured starting from T0-0.83 s in the 10-1000 keV band is 3.8 +/- 0.3 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."