GCN Circular 10358
A. Goldstein (UAH) reports on behalf of the Fermi GBM Team: "At 17:30:57.67 UT on 31 January 2010, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 100131A (trigger 286651859 / 100131730). The Fermi Observatory executed a maneuver following this trigger and tracked the burst location for the next 5 hours, subject to Earth-angle constraints. The on-ground calculated location, using the GBM trigger data, is RA = 120.4, DEC = +16.5 (J2000 degrees, equivalent to 08h 02m, 16d 29'), with an uncertainty of 1.2 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 was 27 degrees. This burst was also independently detected by INTEGRAL SPI-ACS. The GBM light curve consists of a single bright spike with substructure with a duration (T90) of about 6.2 s (8-1000 keV). The time-averaged spectrum from T0 to T0+4.5 s is best fit by a Band function with Epeak = 132.10 +/- 6.28 keV, alpha = -0.63 +/- 0.05, and beta = -2.21 +/- 0.05 (Castor C statistic of 413 for 360 d.o.f.). The event fluence (8-1000 keV) in this time interval is (7.723 +/- 0.130)E-06 erg/cm^2. The 0.128-sec peak photon flux measured starting from T0 in the 8-1000 keV band is 33.8 +/- 1.5 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."