TITLE: GCN CIRCULAR NUMBER: 16189 SUBJECT: GRB 140428B: Fermi GBM observation DATE: 14/04/30 17:52:37 GMT FROM: George A. Younes at USRA/NASA/MSFC George Younes (USRA/MSFC) report on behalf of the Fermi GBM Team: "At 21:44:38.60 UT on 28 April 2014, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 140428B (trigger 420414281 / 140428906, IPN triangulation: Golenetskii et al., GCN 16184). The angle from the Fermi LAT boresight is 111 degrees. This burst also triggered Konus-Wind (Pal'shin et al. GCN #16188). The GBM light curve consists of a single pulse with a duration (T90) of about 0.5 s (50-300 keV). The time-averaged spectrum from T0-0.32 s to T0+19 s is well fit by a power law function with an exponential high-energy cutoff. The power law index is -0.6 +/- 0.2 and the cutoff energy, parameterized as Epeak, is 410 (-80, +134) keV. The event fluence (10-1000 keV) in this time interval is (9.0 +/- 1.0)E-07 erg/cm^2. The 0.064-sec peak photon flux measured starting from T0-0.064 s in the 10-1000 keV band is 17 +/- 2 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."