TITLE:   GCN CIRCULAR
NUMBER:  31506
SUBJECT: GRB 220118A: Fermi GBM detection
DATE:    22/01/20 16:39:29 GMT
FROM:    Boyan A. Hristov at UAH  <bah0046@uah.edu>

Cori Fletcher (USRA) and C. Meegan (UAH) and Boyan A. Hristov
(UAH) report on behalf of the Fermi GBM Team:

"At 18:20:35.84 UT on 18 January 2022, the Fermi Gamma-Ray
Burst Monitor (GBM) triggered and located GRB 220118A
(trigger 664222840 / 220118764), which was also detected by
the Swift BAT/XRT (N. J. Klingler et al. 2022, GCN 31490) and
observed by SWIFT UVOT (A. Belles et al. 2022, GCN 31498).
The Fermi GBM Final Real-time Localization (GCN 31489) is
consistent with the Swift position.

The GBM light curve shows a single peak with a duration (T90)
of about 19 s (50-300 keV).  The time-averaged spectrum from
T0+0.003 s to T0+18.176 s is best fit by a power law function
with an exponential high-energy cutoff.  The power law index is
-1.08 +/- 0.09 and the cutoff energy, parameterized as Epeak,
is 148.30 +/- 17.50 keV.

The event fluence (10-1000 keV) in this time interval is
(3.017 +/- 0.182)E-06.  The 1-sec peak photon flux measured
starting from T0+3.39204 s in the 10-1000 keV band is
4.0 +/- 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/"