GCN Circular 10266
S. McBreen (UCD/MPE) reports on behalf of the Fermi GBM Team: "At 09:49:57.96 UT on 08 December 2009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 091208B (trigger 281958599 / 091208410) which was also detected by the Swift-BAT (Pagani et al. 2009, GCN 10256). The GBM on-ground location is consistent with the Swift position. This burst was also independently detected by INTEGRAL SPI-ACS. The angle from the Fermi LAT boresight is 56 degrees. Moreover, this burst was bright enough to result in a Fermi spacecraft repointing maneuver. The GBM light curve consists of two pulses with a duration (T90) of about 15 s (8-1000 keV). The time-averaged spectrum from T0-0.128 s to T0+14.592 s is well fit by a power law function with an exponential high energy cutoff. The power law index is -1.48 (+0.05/-0.05) and the cutoff energy, parameterized as Epeak, is 144.20 (+18.00/-13.90) keV (CSTAT 829 for 604 d.o.f.). The event fluence (8-1000 keV) in this time interval is (5.8 +/- 0.2)E-06 erg/cm^2. The 0.128 sec peak photon flux measured starting from T0+8.45 s in the 8-1000 keV band is 32.4 +/- 1.1 ph/s/cm^2. A Band function fits the spectrum equally well (CSTAT 827 for 603 d.o.f.) with Epeak= 124.00 (+20.10/-19.40) keV, alpha = -1.44 (+0.07/-0.06) and beta = -2.32 (+0.19/-0.47). The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."