GCN Circular 35563

R. Hamburg (CNRS/IN2P3), S. Dalessi (UAH) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:

"At 01:48:09.44 UT on 18 January 2024, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 240118A (trigger 727235294/240118075),
which was also detected by Fermi-LAT (Bissaldi et al. 2024, GCN 35560
Not found
 
 
).
The Fermi GBM on-ground location (GCN 35558
Not found
 
 
) is consistent with the Fermi-LAT position.

The angle from the Fermi LAT boresight is 64 degrees.

The GBM light curve consists of multiple bright pulses with a duration (T90)
of about 54 s (50-300 keV). The time-averaged spectrum
from T0+0 s to T0+150 s is best fit by 
a Band function with Epeak = 374 +/- 3 keV,
alpha = -0.71 +/- 0.004, and beta = -2.35 +/- 0.02.

The event fluence (10-1000 keV) in this time interval is
(5.81 +/- 0.01)E-04 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+72.5 s in the 10-1000 keV band is 94.6 +/- 0.5 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/"