GCN Circular 28326

S. Lesage (UAH) and C. Meegan (UAH)

report on behalf of the Fermi GBM Team:


"At 13:58:14.66 UT on 29 August 2020, the Fermi Gamma-Ray Burst Monitor
(GBM)

triggered and located GRB 200829A (trigger 620402299 / 200829582)

which was also detected by the Swift Burst Alert Telescope (BAT)

(M. H. Siegel et al. 2020, GCN 28307
Not found
 
 
). GBM initially triggered on a weak

spike ~15-20 s before the very bright emission. The GBM on-ground location

is consistent with the Swift BAT position.


The angle from the Fermi LAT boresight at the GBM trigger time is ~148
degrees.


The GBM light curve shows an exceptionally bright long GRB

with a duration (T90) of about 6.9 s (50-300 keV).

The time-averaged spectrum from T0+16.64 s to T0+25.856 s is

best fit by a Band function with Epeak = 336.8 +/- 4.3  keV,

alpha = -0.43 +/- 0.01, and beta = -2.4 +/- 0.02

The event fluence (10-1000 keV) in this time interval is

(2.069 +/- 0.009)E-04 erg/cm^2.

The 1.024-sec peak photon flux measured starting from T0+19.7 s in

the 10-1000 keV band is 213.9 +/- 1.7 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/"