TITLE: GCN CIRCULAR NUMBER: 9856 SUBJECT: GRB 090829B: Fermi GBM Detection DATE: 09/09/01 02:58:06 GMT FROM: Colleen A. Wilson at NASA/MSFC/NSSTC Colleen A. Wilson-Hodge (NASA/MSFC)reports on behalf of the Fermi GBM Team: "At 16:50:40.13 UT on 29 August 2009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 090829B (trigger 273257442 / 090829702). The on-ground calculated location, using the GBM trigger data, is RA = 355.0, DEC = -9.4 (J2000 degrees, equivalent to 23 h 40 m, -9 d 22'), with an uncertainty of 3.2 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 42 degrees. The GBM light curve consists of two widely spaced peaks with a duration (T90) of about 100 s (8-1000 keV). The time-averaged spectrum from T0-1.5 s to T0+31.2 s is best fit by a Band function with Epeak = 143 +/- 30 keV, alpha = -0.7 +/- 0.2, and beta = -2.4 +/- 0.5 The event fluence (8-1000 keV) in this time interval is (6.4 +/- 0.7)E-6 erg/cm^2. The 1-sec peak photon flux measured starting from T0+4.6 s in the 8-1000 keV band is 3.2 +/- 0.3 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."