GCN Circular 8720
Elisabetta Bissaldi (MPE) reports on behalf of the Fermi GBM Team: "At 10:03:57.15 UT on 23 December 2008, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 081223 (trigger 251719438 / 081223419). The on-ground calculated location, using the GBM trigger data, is RA = 116.7, Dec = 33.5 (J2000 degrees, equivalent to 07h 47m, 33d 30'), with an uncertainty of 6.2 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 28 degrees. This short burst was also independently detected by INTEGRAL SPI-ACS. The GBM light curve consists of a single spike with a duration (T90) of about 890 ms (8-1000 keV). The time-averaged spectrum from T0-0.078 s to T0+0.434 s is adequately fit by a power law function with an exponential high energy cutoff. The power law index is -0.63 +/- 0.10 and the cutoff energy, parameterized as Epeak, is 280 +/- 30 keV (chi squared 334 for 318 d.o.f.). The event fluence (8-1000 keV) in this time interval is (1.20 +/- 0.10)E-06 erg/cm^2. The 64-ms peak photon flux measured starting from T0+0.114 s in the 8-1000 keV band is 22 +/- 3 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."