GCN Circular 15651
A. von Kienlin (MPE) and P. N. Bhat (UAH) report on behalf of the Fermi GBM Team: "At 06:39:24.48 UT on 29 December 2013, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 131229A (trigger 409991967 / 20131229277), which was also detected by the Swift/BAT (Page et al. 2013, GCN 15627 and Konus-Wind Golenetskii et al. 2013, GCN 15639). The GBM on-ground location is consistent with the Swift/XRT position (Evans et al. 2013, GCN 15631) . The angle from the Fermi LAT boresight is 84 degrees. The GBM light curve consists of multiple peaks with a duration (T90) of about 13 s (50-300 keV). The time-averaged spectrum from T0+0.002 s to T0+16.096 s is adequately fit by a power law function with an exponential high-energy cutoff. The power law index is -0.71 +/- 0.02 and the cutoff energy, parameterized as Epeak, is 382.0 +/- 11.6 keV. The event fluence (10-1000 keV) in this time interval is (2.64 +/- 0.05)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+13.216 s in the 10-1000 keV band is 24.0+/-0.4 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."