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GCN Circular 31565

Subject
GRB 220209A: Fermi GBM Detection
Date
2022-02-10T16:40:22Z (2 years ago)
From
Stephen Lesage at Fermi-GBM Team <sjl0014@uah.edu>
S. Lesage (UAH) reports on behalf of the Fermi Gamma-ray Burst Monitor Team:

"At 23:00:50 UT on 09 February 2022, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 220209A (trigger 666140455/220209959)
which was also detected by AGILE (A. Ursi, et al. 2022, GCN 31563)
and GECAM (Y. Q. Zhang, et al. 2022, GCN 31564).
The Fermi GBM Final Real-time Localization (GCN 31561) is
consistent with the GECAM position.

The GBM light curve shows two bright emission episodes
with a duration (T90) of about 201 s (10-1000 keV).

The time-averaged spectrum for the first emission episode
from T0+7.2 to T0+51.2 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -0.92 +/- 0.02 and the cutoff energy,
parameterized as Epeak, is 1097 +/- 118 keV.
The event fluence (10-1000 keV) in this time interval is
(3.48 +/- 0.05)E-05 erg/cm^2.

The time-averaged spectrum for the second emission episode
from T0+159.7 to T0+220.2 s is also best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -0.95 +/- 0.02 and the cutoff energy,
parameterized as Epeak, is 307 +/- 12 keV.
The event fluence (10-1000 keV) in this time interval is
(2.6 +/- 0.04)E-05 erg/cm^2.

The 1-sec peak photon flux measured starting from T0+198.3 s
in the 10-1000 keV band is 17.8 +/- 0.4 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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