TITLE:   GCN CIRCULAR
NUMBER:  31360
SUBJECT: GRB 220101A: Fermi GBM Detection
DATE:    22/01/02 00:16:28 GMT
FROM:    Stephen Lesage at Fermi-GBM Team  <sjl0014@uah.edu>

S. Lesage (UAH) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:

"At 05:17:12 UT on 01 January 2022, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 220101A (trigger 662706616/220101215)
which was also detected by Swift-BAT (A. Tohuvavohu et al. 2022, GCN 31347),
Swift-XRT (J.P. Osborne et al. 2022, GCN 31349), Fermi-LAT (M. Arimoto et
al. 2022, GCN 31350), Swift/UVOT (N. P. M. Kuin et al. 2022, GCN 31351),
and AGILE (A. Ursi et al. 2022, GCN 31354).
The Fermi GBM on-ground location is consistent with the Swift position.

The angle from the Fermi LAT boresight is 38 degrees.

The GBM light curve consists of multiple emission episodes with a duration (T90)
of about 128 s (10-1000 keV). The time-averaged spectrum
from T0-65 to T0+179 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -1.09 +/- 0.02 and the cutoff energy,
parameterized as Epeak, is 330 +/- 15 keV.

The event fluence (10-1000 keV) in this time interval is
(7.7 +/- 0.1)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+90.4 s in the 10-1000 keV band is 11 +/- 0.3 ph/s/cm^2.

A Band function fits the spectrum equally well
with Epeak= 290 +/- 18 keV, alpha = -1.06 +/- 0.02 and beta = -2.3 +/- 0.2.

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/"