TITLE: GCN CIRCULAR NUMBER: 24293 SUBJECT: GRB 190427A: Fermi GBM detection DATE: 19/04/27 17:14:36 GMT FROM: Christian Malacaria at NASA-MSFC/USRA C. Malacaria (NASA-MSFC/USRA), A. von Kienlin (MPE) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 04:34:15.08 UT on 27 04 2019, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 190427A (trigger 578032460 / 190427190). The event was also detected by the Swift/BAT (Tohuvavohu et al. 2019, GCN 24261) The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 106 degrees. The GBM light curve consists of a dominant pulse with following structure and a duration (T90) of about 0.37 s (50-300 keV). The time-averaged spectrum from T0-0.064 s to T0+0.384 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.05 +/- 0.18 and the cutoff energy, parameterized as Epeak, is 246.40 +/- 78.20 keV. The event fluence (10-1000 keV) in this time interval is (4.855 +/- 0.717)E-07 erg/cm^2. The 64-msec peak photon flux measured starting from T0+0.0 s in the 10-1000 keV band is 18.8 +/- 1.1 ph/s/cm^2." The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/