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GCN Circular 30590

GRB 210802A: Fermi GBM detection
2021-08-03T14:58:46Z (3 years ago)
Oliver J Roberts at USRA/NASA <>
O.J. Roberts (USRA/NASA-MSFC) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 20:08:06.49 UT on 02 August 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210802A (trigger 649627691 / 210802839), which was 
also detected by Fermi-LAT (F. Longo et al. 2021, GCN 30589).
The Fermi GBM on-ground location is consistent with the LAT position.

The angle from the Fermi LAT boresight at the GBM trigger time is 51 degrees.

The GBM light curve consists of multiple bright pulses
with a duration (T90) of about 11 s (50-300 keV).
The time-averaged spectrum from T0-0.3 s to T0+12.8 s is
well fit by a power law function with an exponential
high-energy cutoff. The power law index is -0.66 +/- 0.02 and
the cutoff energy, parameterized as Epeak, is 372 +/- 12 keV.

The event fluence (10-1000 keV) in this time interval is
(2.10 +/- 0.03)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+6.6 s in the 10-1000 keV band
is 16.4 +/- 0.3 ph/s/cm^2.

A Band function fits the spectrum equally well
with Epeak= 365 +/- 15 keV, alpha = -0.65 +/- 0.03 and beta = -3.22 +/- 0.75.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:

For Fermi GBM data and info, please visit the official Fermi GBM Support Page:"
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