GRB 241209C: Fermi GBM Observation

"At 07:22:54.60 UT on 09 December 2024, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 241209C (trigger 755421779/241209308), which was also detected by AstroSat (J. Joshi et al. 2024, GCN 38490) and Swift/BAT-GUANO (J. DeLaunay et al. 2024, GCN 38501). The GBM Final Real-time Localization is reported in GCN 38482. The angle from the Fermi LAT boresight is 36 degrees. The GBM light curve consists of a single emission episode with a duration (T90) of about 11 s (50-300 keV). The time-averaged spectrum from T0-4.1 to T0+9.2 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.4 +/- 0.1 and the cutoff energy, parameterized as Epeak, is 270 +/- 20 keV. The event fluence (10-1000 keV) in this time interval is (4 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+4.8 s in the 10-1000 keV band is 3.3 +/- 0.2 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/"