GCN Circular 9813
A. von Kienlin (MPE) reports on behalf of the Fermi GBM Team: "At 10:30:41.85 UT on 15 August 2009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 090815B (trigger 272025043 / Y090815438). The on-ground calculated location, using the GBM trigger data, is RA = 21.4, DEC = 53.4 (J2000 degrees, equivalent to 01h 26m, 53d 24'), with an uncertainty of 5.7 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 82 degrees. The GBM light curve consists of two peaks with a duration (T90) of about 30 s (8-1000 keV). The time-averaged spectrum from T0-7.168 s to T0+23.552 s is well fit by a power law function with an exponential high energy cutoff. The power law index is -1.89 +/- 0.12 and the cutoff energy, parameterized as Epeak, is 15.1 +/- 10.8 keV (chi squared 297 for 238 d.o.f.). The event fluence (8-1000 keV) in this time interval is (5.05 +/- 0.25)E-06 erg/cm^2. The 1.024-sec peak photon flux measured starting from T0+16.384 s in the 8-1000 keV band is 14.4 +/- 0.5 ph/s/cm^2. A Band function fits the spectrum equally well (chi squared 296 for 237 d.o.f.) with Epeak= 18.6 +/- 9.6 keV, alpha = -1.82 +/- 0.19 and beta = -2.7 +/- 0.4. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."