TITLE: GCN CIRCULAR NUMBER: 8822 SUBJECT: GRB 090117C - Fermi GRB Detection DATE: 09/01/18 06:15:23 GMT FROM: Valerie Connaughton at MSFC Valerie Connaughton (UAH) reports on behalf of the Fermi GBM Team: "At 15:10:40.18 UT on 17 Jan 2009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 090117C (trigger 253897842 / 090117632). The on-ground calculated location, using the GBM trigger data, is RA = 117.6, DEC = -40.3 (J2000 degrees, equivalent to 07h 50m, -40d 18'), with an uncertainty of 1.8 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 54 degrees. The GBM light curve consists of a precursor lasting tens of seconds until trigger time, followed by a single episode with substructure lasting a further 35 s. The total duration (T90) between 8 and 1000 keV is about 86 s. The time-averaged spectrum of the main emission from T0-2 s to T0+29 s is best fit by a Band function with Epeak = 247 +/- 41 keV, alpha = -1.0 +/- 0.1, and beta = -2.1 +/- 0.2, giving an 8-1000 keV fluence of (1.1 +/- 0.1) E-5 erg/cm^2. The precursor spectrum from T0-55 sec to T0-6 s is best fit using a power law function with an exponential high energy cutoff. The power law index is -1.3 +/- 0.1 and the cutoff energy, parameterized as Epeak, is 147 +/- 38 keV. The 8-1000 keV fluence of the precursor is (3.9 +/- 0.5) E-6 erg/cm^2. A 1-sec peak photon flux of 4.2 +/- 0.7 ph/s/cm^2 in the 8-1000 keV band is measured starting at T0+22.5 s. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."