TITLE: GCN CIRCULAR NUMBER: 8750 SUBJECT: GRB 081226C: Fermi GBM detection DATE: 08/12/29 15:22:32 GMT FROM: Elisabetta Bissaldi at MPE E. Bissaldi (MPE) and S. McBreen (UCD/MPE) report on behalf of the Fermi GBM Team: "At 03:44:52.41 UT on 26 December 2008, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 081226C (trigger 251955893 / 081226156). The on-ground calculated location, using the GBM trigger data, is RA = 189.4, DEC = 27.8 (J2000 degrees, equivalent to 12h 38m, 27d 48'), with an uncertainty of 3.6 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 54 degrees. This long GRB consists of two main emission pulses plus weak untriggered emission starting at about T0-45 s and lasting about 25 s. The total event duration (T90) is about 60 s (8-1000 keV). The time-averaged spectrum from T0-3.6 s to T0+10.7 s is best fit by a power law function with an exponential high energy cutoff. The power law index is -1.04 +/- 0.11 and the cutoff energy, parameterized as Epeak, is 82 +/- 7 keV (chi squared 395 for 362 d.o.f.). The time-averaged spectrum of the precursor from T0-48.6 s to T0-28.2 s is also well fit by a power law function with an exponential high energy cutoff. The power law index is -1.14 +/- 0.23 and the cutoff energy, parameterized as Epeak, is 71 +/- 11 keV (chi squared 370 for 363 d.o.f.). The event fluence (8-1000 keV) from T0-3.6 s to T0+10.7 is (2.32 +/- 0.24)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+6.6 s in the 8-1000 keV band is 4.5 +/- 0.8 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."