GCN Circular 25575

S. Lesage (UAH), S. Poolakkil (UAH), C. Fletcher (USRA), C. Meegan (UAH)
and A. Goldstein (USRA) report on behalf of the Fermi GBM Team:

"At 19:55:53.13 UT on 29 August 2019, the Fermi Gamma-Ray Burst Monitor
(GBM)
triggered and located GRB 190829A (trigger 588801358 / 190829830),
which was also detected by the Swift/XRT (Dichiara et al. 2019, GCN 25552
Not found
 
 
)
The Fermi GBM Final Real-time Localization (GCN 25551
Not found
 
 
) is consistent with
the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 33
degrees.

The GBM light curve shows an initial pulse followed by a brighter
peak, with a duration (T90) of about 63 s (50-300 keV).
The time-averaged spectrum for the initial pulse,
from T0s to T0+4.0 s, is best fit by
a power law function with an exponential
high-energy cutoff.  The power law index is -1.41 +/- 0.08 and
the cutoff energy, parameterized as Epeak, is 130 +/- 20 keV.
The time-averaged spectrum for the second pulse,
from T0+47.1 s to T0+61.4 s, is best fit by
a Band function with Epeak = 11 +/- 1 keV,
alpha = -0.92 +/- 0.62, and beta = -2.51 +/- 0.01.

The fluence (10-1000 keV) of the two peaks is
(1.267 +/- 0.015)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+51.2 s in the 10-1000 keV band
is ~25.6 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/"