GRB 200809B: Fermi GBM detection

"At 15:41:27.13 UT on 09 August 2020, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 200809B (trigger 618680492 / 200809654) which was also detected by the Swift/BAT-GUANO (Tohuvavohu et al. 2020, GCN 28237) The Fermi GBM Final Real-time Localization (GCN 28236) is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 111 degrees. This burst was also independently detected by MAXI/GSC (GCN 28240) and AstroSat CZTI (GCN 28238). The GBM light curve consists of a single peak with a duration (T90) of about 17 s (50-300 keV). The time-averaged spectrum from T0 s to T0+17.6 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.5 +/- 0.3 and the cutoff energy, parameterized as Epeak, is 682 +/- 246 keV. The event fluence (10-1000 keV) in this time interval is (3.717 +/- 0.387)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0-0.13 s in the 10-1000 keV band is 4.7 +/- 0.3 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/"