GCN Circular 8876
A. Goldstein (UAH) and A.J. van der Horst (NASA/MSFC/ORAU) report on behalf of the Fermi GBM Team: "At 02:09:21.15 UT on 31 January 2009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 090131 (trigger 255060563 / 090131090). The on-ground calculated location, using the GBM trigger data, is RA = 353.0, DEC = +16.4 (J2000 degrees, equivalent to 23h 32m, 16d 26'), with a statistical uncertainty of less than 1 degree (radius, 1-sigma containment) and an additional systematic error which is currently estimated to be 2 to 3 degrees. The angle from the Fermi LAT boresight is 40 degrees. The GBM light curve consists of two emission pulses, each with substructure and separated by a period of no significant emission above background. The total duration (T90) is about 36.4 s (8-1000 keV). The time-averaged spectrum from T0+0.0 s to T0+42.2 s is best fit by a Band function with Epeak = 58.4 +/- 3.9 keV, alpha = -1.27 +/- 0.07, and beta = -2.26 +/- 0.05 (chi-square 597.4 for 453 d.o.f.). The event fluence (8-1000 keV) in this time interval is (2.23 +/- 0.17)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+6.4 s in the 8-1000 keV band is 47.9 +/- 10.0 ph/s/cm^2. The spectral and temporal analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."