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/." View this GCN Circular online at https://gcn.nasa.gov/circulars/35586. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...