TITLE: GCN CIRCULAR NUMBER: 15129 SUBJECT: GRB 130828A: Fermi GBM detection DATE: 13/08/29 03:32:12 GMT FROM: Andrew Collazzi at NASA/MSFC/ORAU Andrew C. Collazzi (NASA/ORAU) reports on behalf of the Fermi GBM Team: "At 07:20:00.15 UT on 28 August 2013, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 130828A (trigger 399367203 / 130828.306). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 258.14, Dec = +29.76 (J2000 degrees, equivalent to J2000 17h 12m, +29d 45' ), with a statistical uncertainty of 1.0 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which is currently estimated to be 2 to 3 degrees). The angle from the Fermi LAT boresight is 46 degrees. The burst was strong enough to trigger an Automatic Repointing Request (ARR) on the Fermi spacecraft. The GRB position was placed in the center of the LAT Field-of-view for 2.5 hours (subject to Earth angle constraints). The GBM light curve shows consists of several pulses, and is possibly on top of a particle event. We find a duration (T90) of about 159 +/- 23 s (50-300 keV). We find the 1.024s peak flux during this time to be (7.39 +/- 0.37) ph/s/cm^2. The time-averaged spectrum from T0-4.10 to T0+159.75 s is best fit by a Band function with Epeak = 320.7 +/- 21.0 keV, alpha = -0.90 +/- 0.03, and beta = -2.22 +/- 0.03. The fluence (10-1000 keV) in this time interval is (6.05 +/- 0.09)E-05 erg/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."