GCN Circular 25435
B. Mailyan, S. Lesage and C. Meegan (all UAH) report on behalf of the Fermi GBM Team: "At 17:10:34.08 UT on 21 August 2019, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 190821A (trigger 588100239/ 190821716), which was also detected by the Swift/BAT (D'Ai et al. 2019, GCN 25427). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 85 degrees. The GBM lightcurve shows an initial bright pulse followed by longer duration emission containing multiple peaks. with a duration (T90) of about 60 s (50-300 keV). The time-averaged spectrum from T0-4 s to T0+34 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.7 +/- 0.15 and the cutoff energy, parameterized as Epeak, is 29 +/- 6 keV. The event fluence (10-1000 keV) in this time interval is (2.54 +/- 0.17)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T-0.128 s in the 10-1000 keV band is 4.9 +/- 0.25 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/"