TITLE: GCN CIRCULAR NUMBER: 15113 SUBJECT: GRB 130821A: Fermi GBM Detection DATE: 13/08/22 16:51:18 GMT FROM: Peter Jenke at MSFC P. Jenke (UAH) reports on behalf of the Fermi GBM Team: "At 16:10:28.011 UT on August 21 2013, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 130821A (trigger 398794231/130821674), which resulted in an Autonomous Repoint Request (ARR) that was accepted and the LAT slewed to the GBM position. The GBM on-ground location, using the Fermi GBM trigger data, is RA = 308.2, Dec = -15.5 (J2000 degrees, equivalent to J2000 20h 32m, -15d 30'), with a statistical uncertainty of 1 degree (radius, 1-sigma containment, statistical only; there is additionally a systematic error which is currently estimated to be 2 to 3 degrees). The angle of the burst direction to the Fermi LAT boresight is 37 degrees. The GBM light curve consists of multiple peaks with a duration (T90) of about 84 s (50-300 keV). The time-averaged spectrum from T0-3 s to T0+49 s is well fit by a Band function with Epeak of 165 +/- 5 keV, Alpha = -0.54 +/- 0.03 and Beta = -2.01 +/- 0.02. The event fluence (10-1000 keV) in this time interval is (6.60 +/- 0.08)E-05 erg/cm^2. The 1.0-sec peak photon flux measured starting from T0+32 s in the 10-1000 keV band is 27.6 +/- 0.4 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog." [GCN OPS NOTE(25aug13); Per operator's request, the "A" suffix was added to the GRB name.]