GCN Circular 21033
M. Stanbro (UAH), A. von Kienlin (MPE) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 10:12:30.75 UT on 24 April 2017, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 170424A (trigger 514721555 / 170424425) which was also detected by the Fermi-LAT (N. Omodei et al. 2017, GCN 21032). The GBM on-ground location is consistent with the Fermi-LAT position. This burst was also independently detected by INTEGRAL SPI-ACS. The GBM light curve consists of one episode with a duration (T90) of about 52 s (50-300 keV). The time-averaged spectrum from T0+1.54 s to T0+55.81 s is best fit by a Band function with Epeak = 464 +/- 39 keV, alpha = -0.85 +/- 0.03, and beta = -2.00 +/- 0.09. The event fluence (10-1000 keV) in this time interval is (3.07 +/- 0.05)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+23.5 s in the 10-1000 keV band is 4.8 +/- 0.2 ph/s/cm^2. A power law function with an exponential high-energy cutoff fits the spectrum equally well. The power law index is -0.89 +/- 0.02 and the cutoff energy, parameterized as Epeak, is 570 +/- 33 keV. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."