GCN Circular 28206
R. Hamburg (UAH) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 03:34:26.00 UT on 03 August 2020, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 200803A (trigger 618118471 / 200803149) which was also detected by the Fermi/LAT (Cutini et al. 2020, GCN 28203). The Fermi GBM Final Real-time Localization (GCN 28196) is consistent with the LAT position. An x-ray afterglow candidate has been detected by the Swift/XRT (GCN 28205), and a potential optical counterpart has also been reported by MASTER (GCN 28202). The angle from the Fermi LAT boresight at the GBM trigger time is ~39 degrees. The GBM light curve consists of two main pulses with a duration (T90) of about 119 s (50-300 keV). The time-averaged spectrum of the first pulse, from T0-4 s to T0+14 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.67 +/- 0.04 and the cutoff energy, parameterized as Epeak, is 302 +/- 13 keV. The event fluence (10-1000 keV) in this time interval is (1.12 +/- 0.03)E-05. The time-averaged spectrum of the second pulse, from T0+85 s to T0+118 s is also best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.13 +/- 0.02 and the cutoff energy, parameterized as Epeak, is 223 +/- 8 keV. The event fluence (10-1000 keV) in this time interval is (1.84 +/- 0.03)E-05. The 1-sec peak photon flux measured starting from T0+112 s in the 10-1000 keV band is 10.8 +/- 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/"