TITLE: GCN CIRCULAR NUMBER: 35955 SUBJECT: GRB 240317B: Fermi GBM Observation DATE: 24/03/18 16:26:15 GMT FROM: rachel.hamburg@ijclab.in2p3.fr R. Hamburg (CNRS/IN2P3/IJCLab) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 10:54:24.02 UT on 17 March 2024, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 240317B (trigger 732365669/240317454), which was also detected by Swift/BAT-GUANO (DeLaunay et al. 2024, GCN 35948). The Fermi GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight is 89 degrees. The GBM light curve shows one main emission episode with a duration (T90) of about 35 s (50-300 keV). The time-averaged spectrum from T0-6.1 to T0+32.8 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.6 +/- 0.3 and the cutoff energy, parameterized as Epeak, is 76 +/- 9 keV. The event fluence (10-1000 keV) in this time interval is (1.9 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+3.0 s in the 10-1000 keV band is 2.3 +/- 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/" View this GCN Circular online at https://gcn.nasa.gov/circulars/35955. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...