TITLE:   GCN CIRCULAR
NUMBER:  31340
SUBJECT: GRB 211229A: Fermi GBM observation
DATE:    21/12/30 05:30:27 GMT
FROM:    Peter Veres at UAH  <veresp@gmail.com>

P. Veres and C. Meegan (both UAH)
report on behalf of the Fermi GBM Team:

"At 03:29:15.90 UT on 29 December 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 211229A (trigger 662441360 / 211229145),
which was also detected by the Swift/BAT-GUANO (Tohuvavohu et al, GCN 31334).
The Fermi GBM Final Real-time Localization (GCN 31329) is consistent
with the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 95 degrees.

The GBM light curve shows multiple pulses
with a duration (T90) of about 120 s (50-300 keV).
The time-averaged spectrum from T0-10 s to T0+147 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -1.24 +/- 0.03 and
the cutoff energy, parameterized as Epeak, is 280 +/- 27 keV.

The event fluence (10-1000 keV) in this time interval is
(3.07 +/- 0.11)E-5 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+53.2 s in the 10-1000 keV band
is 3.74 +/- 0.28 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/"