TITLE: GCN CIRCULAR NUMBER: 8622 SUBJECT: GRB 081204B: Fermi GBM detection DATE: 08/12/05 15:48:57 GMT FROM: Elisabetta Bissaldi at MPE E. Bissaldi and A. von Kienlin (MPE) report on behalf of the Fermi GBM Team: "At 12:24:25.79 UT on 4 December 2008, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 081204B (trigger 250086266 / 081204517). The on-ground calculated location, using the GBM trigger data, is RA = 181.4, DEC = +32.1 (J2000 degrees, equivalent to 12h 06m, 32d 06'), with an uncertainty of 7.3 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 46 degrees. This short GRB consists of a single pulse with a duration (T90) of about 320 ms (8-1000 keV). The time-averaged spectrum from T0-0.077 s to T0+0.115 s is best fit by a simple power law function with index -1.18 +/- 0.05 (chi squared 439 for 477 d.o.f.). The event fluence (8-1000 keV) in this time interval is (4.88 +/- 0.13)E-07 erg/cm^2. The peak photon flux on the 64 ms timescale measured starting from T0-0.077 s in the 8-1000 keV band is 16.3 +/- 0.6 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."