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GCN Circular 33034

Subject
GRB 221209A: Fermi GBM observation
Date
2022-12-09T15:04:36Z (a year ago)
From
Elisabetta Bissaldi at INFN,Bari <elisabetta.bissaldi@ba.infn.it>
E. Bissaldi (Politecnico and INFN Bari)
reports on behalf of the Fermi GBM Team:


"At 05:50:24.85 UT on 9 December 2022,
the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 221209A
(trigger 692257829 / 221209243).
The Fermi GBM Final Real-time Localization
is reported in GCN 33031.

The angle from the Fermi LAT boresight
at the GBM trigger time is 97 degrees.


The GBM light curve consists of a single
bright emission episode with a duration (T90)
of about 4 s (50-300 keV).
The time-averaged spectrum from T0 to T0+7 s is
best fit by a Band function with
Epeak = 325 +/- 12 keV, alpha = -0.62 +/- 0.02,
and beta = -2.08 +/- 0.03.

The event fluence (10-1000 keV) in this
time interval is (3.35 +/- 0.03)E-05 erg/cm^2.
The 1-sec peak photon flux measured starting
from T0+1.2 in the 10-1000 keV band
is 67.1 +/- 0.6 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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