TITLE: GCN CIRCULAR NUMBER: 35563 SUBJECT: GRB 240118A: Fermi GBM Observation DATE: 24/01/18 16:07:47 GMT FROM: rachel.hamburg@ijclab.in2p3.fr 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). The Fermi GBM on-ground location (GCN 35558) 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/" View this GCN Circular online at https://gcn.nasa.gov/circulars/35563. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...