TITLE:   GCN CIRCULAR
NUMBER:  35444
SUBJECT: GRB231230A: Fermi GBM Observation
DATE:    23/12/30 18:40:14 GMT
FROM:    Cori Fletcher at USRA <cfletcher@usra.edu>

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

"At 01:29:10.05 UT on 30 December 2023, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB231230A (trigger 725592555/231230062).
which was also detected by Swift-BAT (Moss et al. 2023, GCN 35436).
The Fermi GBM Real-time Localization (GCN 35434) is consistent with the Swift-BAT position.

The angle from the Fermi LAT boresight is 157 degrees.

The GBM light curve consists of multiple spikes with a duration (T90)
of about 17 s (50-300 keV). The time-averaged spectrum
from T0-2.6 to T0+17.9 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -1.2 +/- 0.2 and the cutoff energy,
parameterized as Epeak, is 220 +/- 40 keV.

The event fluence (10-1000 keV) in this time interval is
(6.1 +/- 0.5)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+9.3 s in the 10-1000 keV band is 5 +/- 1 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/"