TITLE: GCN CIRCULAR NUMBER: 9849 SUBJECT: GRB090829: Fermi GBM Detection DATE: 09/08/31 01:54:07 GMT FROM: Colleen A. Wilson at NASA/MSFC/NSSTC Colleen A. Wilson-Hodge reports on behalf of the Fermi GBM Team: "At 16:07:38.86 UT on 29 August 2009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 090829 (trigger 273254860 / 090829672). The on-ground calculated location, using the GBM trigger data, is RA = 329.2, DEC = -34.2 (J2000 degrees, equivalent to 21 h 57 m, 34 d 11'), with an 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 from the Fermi LAT boresight is 47 degrees. This burst triggered an automatic repoint of Fermi. The GBM light curve, with a duration (T90) of about 85 s (8-1000 keV), consists of a weak precursor followed by a bright peak. The time-averaged spectrum from T0-6.1 s to T0+92 s is adequately fit by a Band function with Epeak = 183 +/- 31 keV, alpha = -1.44 +/- 0.04, and beta = -2.1 +/- 0.1 The event fluence (8-1000 keV) in this time interval is (1.02 +/- 0.02)E-4 erg/cm^2. The 1-sec peak photon flux measured starting from T0+46 s in the 8-1000 keV band is 51.5 +/- 0.9 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."