TITLE:   GCN CIRCULAR
NUMBER:  31660
SUBJECT: GRB 220228A: Fermi GBM observation
DATE:    22/02/28 22:26:02 GMT
FROM:    Joshua Wood at MSFC/Fermi-GBM  <joshua.r.wood@nasa.gov>

J. Wood (NASA/MSFC) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 10:30:05.92 UT on 28 Feb 2022, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 220228A (trigger 667737010 / 220228438)
which was also detected by the Fermi LAT (N. Omodei et al. 2022, GCN 31659).
The GBM on-ground location (GCN 31658) is consistent with the LAT position.

The GBM light curve consists of a single pulse
with a duration (T90) of about 12.5 s (50-300 keV).
The time-averaged spectrum from T0-7 s to T0+6 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is 1.7 +/- 0.2 and
the cutoff energy, parameterized as Epeak, is 106 +/- 46 keV

The event fluence (10-1000 keV) in this time interval is
((1.1 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0-0.5 s in the 10-1000 keV band
is 3.1 +/- 0.2 ph/s/cm^2.

A power law function fits the spectrum equally well
with index -1.9 +/- 0.1.

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/"