TITLE: GCN CIRCULAR NUMBER: 27531 SUBJECT: SGR 1935+2154: Fermi GBM observation DATE: 20/04/10 21:37:38 GMT FROM: Peter Veres at UAH P. Veres (UAH), E. Bissaldi (Politecnico and INFN Bari) and M. S. Briggs (UAH) report on behalf of the Fermi GBM Team: "At 09:43:54.30 UT on 10 April 2020, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located an outburst from SGR 1935+2154 (trigger 608204639 / 200410405) which was also detected by the Konus-Wind (IPN) (Svinkin at al., GCN 27527). The GBM on-ground location is consistent with the known position of the SGR. The trigger was classified as a GRB by the flight software, but it is in fact from SGR 1935+2154. The angle from the Fermi LAT boresight at the GBM trigger time is 105 degrees. The light curve shows a short bright peak with a duration (T90) of about 128 ms (50-300 keV). The time-averaged spectrum from T0-64 ms to T0+192 ms is best fit by a power law function with an exponential high-energy cutoff. The power law index is 0.70 +/- 0.10 and the cutoff energy, parameterized as Epeak, is 32.7 +/- 0.3 keV The event fluence (10-1000 keV) in this time interval is (2.57 +/- 0.03)E-6 erg/cm^2. The 64-ms peak photon flux measured starting from T0 in the 10-1000 keV band is 489 +/- 9 ph/s/cm^2. We note that we see indications of saturation of only the TTE data at the brightest part of the pulse. 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/"