TITLE:   GCN CIRCULAR
NUMBER:  29161
SUBJECT: GRB 201223A: Fermi GBM Detection
DATE:    20/12/23 23:53:30 GMT
FROM:    Joshua Wood at MSFC/Fermi-GBM  <joshua.r.wood@nasa.gov>

J. Wood (NASA/MSFC) reports on behalf of the Fermi GBM Team:

"At 17:58:25.69 UT on 23 December 2020, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 201223A (trigger 630439110 / 201223749)
which was also detected by the Swift/BAT and Swift/XRT
(Gropp et al. 2020, GCN 29158). The GBM
on-ground location is consistent with the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 63 degrees.

The GBM light curve shows multiple peaks
with a duration (T90) of about 33 s (50-300 keV).
The time-averaged spectrum from T0-17 s to T0+13 s is
best fit by a Band function with Epeak = 86 +/- 12 keV, 
alpha = 0.14 +/- 0.38 and beta = -2.6 +/- 0.4.
A power law function with an exponential
high-energy cutoff fits the spectrum equally well.
The power law index is -0.14 +/- 0.24 and
the cutoff energy, parameterized as Epeak, is 99 +/- 8 keV.

The event fluence (10-1000 keV) in this time interval is
(2.1 +/- 0.3)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+4.1 s in the 10-1000 keV band
is 2.4 +/- 0.2 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/"