TITLE:   GCN CIRCULAR
NUMBER:  35586
SUBJECT: GRB 240118C: Fermi GBM Observation
DATE:    24/01/20 01:01:56 GMT
FROM:    Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov>

V. Sharma (NASA-GSFC/UMBC) and C. Meegan (UAH) report on behalf of the 
Fermi Gamma-ray Burst Monitor Team:

"At 17:23:23.93 UT on 18 January 2024, the Fermi Gamma-ray Burst Monitor (GBM) 
triggered and located GRB 240118C (trigger 727291408/240118725), which was also 
detected by Swift/BAT-GUANO (DeLaunay et al. 2024, GCN 35581).
The Fermi Final Real-time Localization is reported in GCN 35576.

The angle from the Fermi LAT boresight is 90 degrees.

The GBM light curve consists of multiple pulses with a duration (T90)
of about 31 s (50-300 keV). The time-averaged spectrum from 
T0-0.6 to T0+32.5 s is best fit by a power law function with 
an exponential high-energy cutoff.
The power law index is -1.39 +/- 0.03 and the cutoff energy,
parameterized as Epeak, is 144 +/- 10 keV.

The event fluence (10-1000 keV) in this time interval is (1.23 +/- 0.04)E-05 erg/cm^2. 
The 1-sec peak photon flux measured starting from T0+29.7 s in the 10-1000 keV band 
is 13.6 +/- 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/."