GCN Circular 18190
O.J. Roberts (UCD) reports on behalf of the Fermi GBM team: "At 09:44:20.33 UT on August 21st 2015, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 150821A (trigger 461843064/150821406), which was also detected by Swift (Troja et al. 2015, GCN 18186). The trigger resulted in an Autonomous Repoint Request (ARR) due to the high peak flux of the GRB. This ARR was accepted and the spacecraft slewed to the GBM in-flight location. Both the GBM in-flight and on-ground locations are consistent with the Swift position. The angle of the burst direction to the Fermi LAT boresight is 57 degrees. The GBM light curve consists of a FRED-like burst, with two unresolved peaks and a duration of about 103 s (50-300 keV). The time-averaged spectrum from T0-2.0s to T0+101.4s is well fit by a Band function with Epeak = 322 +/- 18 keV, Alpha =-1.21 +/- 0.01 and Beta = -2.27 +/- 0.10. The event fluence (10-1000 keV) in this time interval is (6.87 +/- 0.08)E-05 erg/cm^2. The 1.024 s peak photon flux measured starting from T0+17.1s in the 10-1000 keV band is 11.1 +/- 0.3 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."