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GCN Circular 25575

Subject
GRB 190829A: Fermi GBM detection
Date
2019-08-30T12:43:01Z (5 years ago)
From
Suraj Poolakkil at UAH <sp0076@uah.edu>
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)
The Fermi GBM Final Real-time Localization (GCN 25551) 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/"
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