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GCN Circular 33077

Subject
GRB 221216A: Fermi GBM observation
Date
2022-12-17T09:17:16Z (a year ago)
From
Rachel Dunwoody at UCD <rachel.dunwoody@ucdconnect.ie>
R. Dunwoody (UCD), J. Mangan (UCD) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 11:21:18.18 UT on 16 December 2022, the Fermi Gamma-Ray Burst Monitor
(GBM)
triggered and located GRB 221216A (trigger 692882483 / 221216473)
which was also detected by the Swift/BAT (Dichiara et al. 2022, GCN 33067)
The Fermi GBM Final Real-time Localization (GCN 33066) is consistent with
the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 101
degrees.

The GBM light curve shows multiple peaks
with a duration (T90) of about 184 s (50-300 keV).
The time-averaged spectrum from T0-15 s to T0+173 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -0.58 +/- 0.18 and
the cutoff energy, parameterized as Epeak, is 94.6 +/- 8.4 keV.
It is fit equally well with a Band function with
Epeak = 82.4 +/- 12.1 keV, alpha = -0.4 +/- 0.3, and beta = -2.5 +/- 0.3.

The event fluence (10-1000 keV) in this time interval is
(6.31 +/- 0.40)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+3 s in the 10-1000 keV band
is 3.7 +/- 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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