TITLE:   GCN CIRCULAR
NUMBER:  34249
SUBJECT: GRB 230723B: Fermi GBM observation
DATE:    23/07/24 14:00:22 GMT
FROM:    Joe Mangan at IJCLab <joseph.mangan@ijclab.in2p3.fr>

J.Mangan (CNRS/IJCLab) and C. Meegan (UAH) report on behalf of the Fermi GBM Team:

At 11:42:33.03 UT on 23 July 2023, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 230723B (trigger 711805358 / 230723488),
which was also detected by Swift BAT (K. L. Page et al. 2023, GCN 34234).
The Fermi GBM on-ground location is consistent with the Swift BAT position.

The angle from the Fermi LAT boresight at the GBM trigger time is 78 degrees.

The GBM light curve consists of a single peak
with a duration (T90) of about 10 s (50-300 keV).
The time-averaged spectrum from T0-2 s to T0+9 s is
best fit by a power law function with an exponential
high-energy cutoff. The power law index is -0.9 +/- 0.1 and
the cutoff energy, parameterized as Epeak, is 59.1 +/- 2.7 keV.

The event fluence (10-1000 keV) in this time interval is
(3.8 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+1.2 s in the 10-1000 keV band
is 7.8 +/- 0.4 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/