TITLE: GCN CIRCULAR NUMBER: 10702 SUBJECT: GRB 100427A: Fermi GBM detection DATE: 10/04/29 00:31:46 GMT FROM: Adam Goldstein at Fermi-GBM/UAH A. Goldstein (UAH) and D. Gruber (MPE) report on behalf of the Fermi GBM Team: "At 08:32:08.71 UT on 27 April 2010, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 100427A (trigger 294049930 / 100427356), which was also detected by the Swift-BAT (J.R. Cummings et al. 2010, GCN 10699). The GBM on-ground location is consistent with the Swift-BAT position. The angle from the Fermi LAT boresight is 29 degrees. The GBM light curve consists of a single pulse with multiple peaks with a duration (T90) of about 24 s (8-1000 keV). The time-averaged spectrum from T0-4.1 s to T0+11.3 s is best fit by a power law function with an exponential high energy cutoff. The power law index is -1.02 +0.12/-0.11 and the cutoff energy, parameterized as Epeak, is 121.0 +15.4/-11.8 keV (Castor C-Stat 519 for 484 d.o.f.). The event fluence (8-1000 keV) in this time interval is (3.01 +/- 0.13)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+5.18 s in the 8-1000 keV band is 4.79 +/- 0.24 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."