GCN Circular 14435
Arne Rau (MPE) reports on behalf of the Fermi GBM Team: "At 12:56:32.99 UT on 20 April 2013, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 130420B (trigger 388155395 / 130420539), which was also detected by Swift/BAT (Oates et al., GCN 14411). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight is about 50 degrees. The GBM light curve shows a single pulse with a duration (T90) of about 16 s (50-300 keV). The time-averaged spectrum from T0-4 s to T0+4 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is 0.24 +/- 0.25 and the cutoff energy, parameterized as Epeak, is 91 +/- 9 keV. The event fluence (10-1000 keV) in this time interval is (1.04 +/- 0.08)E-07 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.0 s in the 10-1000 keV band is 2.6 +/- 0.2 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."