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
Not found
 
 
).
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/"