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GCN Circular 29628

Subject
GRB 210305A: Fermi GBM observation
Date
2021-03-08T22:42:28Z (3 years ago)
From
Peter Veres at UAH <veresp@gmail.com>
P. Veres, B. Hristov and C. Meegan (all UAH)
report on behalf of the Fermi GBM Team:

"At 19:02:59.40 UT on 05 March 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210305A (trigger 636663784 / 210305794),
which was also detected by the Swift/BAT/XRT (D'Ai et al., GCN 29595).
The GBM on-ground location is consistent with the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 90 degrees.

The GBM light curve shows multiple overlapping pulses
with a duration (T90) of about 61.7 s (50-300 keV).
The time-averaged spectrum from T0-11.3 s to T0+59.4 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -0.17 +/- 0.09 and
the cutoff energy, parameterized as Epeak, is 98 +/- 3 keV.

A Band function fits the spectrum equally well
with Epeak= 95 +/- 4 keV, alpha = -0.11 +/- 0.11 and beta = -3.25 +/- 0.45.

The event fluence (10-1000 keV) in this time interval is
(9.4 +/- 0.2)E-6 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+6.3 s in the 10-1000 keV band
is 4.6 +/- 0.3 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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