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GCN Circular 29709

Subject
GRB 210323A: Fermi GBM detection
Date
2021-03-24T13:30:47Z (3 years ago)
From
Rachel Hamburg at UAH <rkh0007@uah.edu>
R. Hamburg (UAH) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 22:02:18.40 UT on 23 March 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210323A (trigger 638229743 / 210323918),
which was also detected by the Swift/BAT and Swift/XRT (Gropp et al. 2021,
GCN 29699). The GBM on-ground location is consistent with the Swift
position.

The angle from the Fermi LAT boresight at the GBM trigger time is 92
degrees.

The GBM light curve shows a single-peaked structure
with a duration (T90) of about 1 s (50-300 keV).
The time-averaged spectrum from T0-0.064 s to T0+0.192 s is
best fit by a power law function with an exponential
high-energy cutoff. The power law index is -0.97 +/- 0.05 and
the cutoff energy, parameterized as Epeak, is 2.1 +/- 0.4 MeV.
A Band function also fits the spectrum with Epeak = 2.1 +/- 0.5 MeV,
alpha = -0.97 +/- 0.05 and beta = -3.02 +/- 1.02.

The event fluence (10-1000 keV) in this time interval is
(1.2 +/- 0.1)E-06 erg/cm^2. The 64-ms peak photon flux measured
starting from T0+0.064 s in the 10-1000 keV band
is 21.3 +/- 1.5 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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