GCN Circular 33077
R. Dunwoody (UCD), J. Mangan (UCD) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 11:21:18.18 UT on 16 December 2022, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 221216A (trigger 692882483 / 221216473) which was also detected by the Swift/BAT (Dichiara et al. 2022, GCN 33067) The Fermi GBM Final Real-time Localization (GCN 33066) is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 101 degrees. The GBM light curve shows multiple peaks with a duration (T90) of about 184 s (50-300 keV). The time-averaged spectrum from T0-15 s to T0+173 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.58 +/- 0.18 and the cutoff energy, parameterized as Epeak, is 94.6 +/- 8.4 keV. It is fit equally well with a Band function with Epeak = 82.4 +/- 12.1 keV, alpha = -0.4 +/- 0.3, and beta = -2.5 +/- 0.3. The event fluence (10-1000 keV) in this time interval is (6.31 +/- 0.40)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+3 s in the 10-1000 keV band is 3.7 +/- 0.3 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/"