TITLE: GCN CIRCULAR NUMBER: 8432 SUBJECT: GRB 081021: Fermi GBM detection DATE: 08/10/28 16:27:20 GMT FROM: Andreas von Kienlin at MPE A. von Kienlin (MPE) and E. Bissaldi (MPE) report on behalf of the Fermi GBM Team: "At 09:33:28 UT on 21 October 2008, the Fermi GBM triggered and located GRB 081021 (trigger 246274409 / 081021398). The on-ground calculated location, using the GBM trigger data, is RA = 197.9, DEC = -25.1 (J2000 degrees, equivalent to 13h 12m, +25d 06'), with an uncertainty of 2.2 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 125 degrees. This GRB has one isolated peak, which is about 25 sec long. The time-averaged spectrum (10-1000 keV) from T0-3.8 s to T0+15.6 s is best fit by a Band function with Epeak = 117 +/- 11 keV, alpha = 0.11 +/- 0.25, and beta = -2.8 +/- 0.4. The fluence (10-1000 keV) in this time interval from the Band model is (5.3 +/- 0.6)E-06 erg/cm^2. The 1 sec peak photon flux measured starting from T0+2.3 s in the 10-1000 keV band is 4.2 +/- 0.9 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."