GCN Circular 8961
E.Bissaldi (MPE) and A. von Kienlin (MPE) report on behalf of the Fermi GBM Team: "At 04:00:58.60 UT on 07 March 2009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 090307B (trigger 258091199 / 090307167). The on-ground calculated location, using the GBM trigger data, is RA = 158.6, DEC = -14.6 (J2000 degrees, equivalent to 10h 34m, -14d 36'), with an uncertainty of 9.7 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 83 degrees. This long GRB consists of one main FRED-like pulse with substructure, rising at T0-6 s and with a duration (T90) of about 30 s (8-1000 keV). T50 is about 15 s (8-1000 keV). The time-averaged spectrum from T0-6 s to T0+10.4 s is best fit by a power law function with an exponential high energy cutoff. The power law index is -0.7 +/- 0.3 and the cutoff energy, parameterized as Epeak, is 212 +/- 80 keV (chi squared 346 for 357 d.o.f.). The event fluence (8-1000 keV) in this time interval is (1.7 +/- 0.4)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0-5 s in the 8-1000 keV band is 1.80 +/- 0.12 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."