TITLE: GCN CIRCULAR NUMBER: 10225 SUBJECT: GRB 091126B: Fermi GBM detection DATE: 09/12/01 16:57:03 GMT FROM: Sheila McBreen at MPE S. McBreen (UCD/MPE) reports on behalf of the Fermi GBM Team: "At 09:19:48.53 UT on 26 November 2009, the Fermi Gamma-Ray Burst Monitor triggered and located a short burst GRB 091126B (trigger 280919990/091126389). The on-ground calculated location, using the GBM trigger data, is RA = 47.4, DEC = 31.5 (J2000 degrees, equivalent to 03 h 10 m, 31 d 30 '), with an uncertainty of 14.3 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 60 degrees. This burst was also independently detected by INTEGRAL SPI-ACS. The GBM light curve consists of one pulse with a duration of about 30 ms (8-1000 keV). The time-averaged spectrum from T0-0.016 s to T0+0.016 s is adequately fit by a power law function with an exponential high energy cutoff. The power law index is -0.23 (+0.32/-0.23) and the cutoff energy, parameterized as Epeak, is 731 (+229/-165) keV (CSTAT 753 for 846 d.o.f.). The event fluence (8-1000 keV) in this time interval is (2.2 +/- 0.02)E-07 erg/cm^2. The 16 ms peak photon flux measured starting from T0-0.008 s in the 8-1000 keV band is 20.5 +/- 1.3 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."