GCN Circular 31263
E. Bissaldi (Politecnico and INFN Bari) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 06:45:52.06 UT on 16 December 2021, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 211216A (trigger 661329957 / 211216282), which was also detected by the Swift/BAT-GUANO (Tohuvavohu et al. 2021, GCN 31250) and by GECAM-B (Xue et al. 2021, GCN 31240). The GBM on-ground location is reported in GCN 31237. The GBM light curve shows a FRED-like emission episode with a duration (T90) of about 20 s (50-300 keV). The time-averaged spectrum from T0 to T0+20 s is well fit by a power law function with an exponential high-energy cutoff. The power law index is -0.47 +/- 0.05 and the cutoff energy, parameterized as Epeak, is 208 +/- 7 keV. The event fluence (10-1000 keV) in this time interval is (9.16 +/- 0.02)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+6.3 s in the 10-1000 keV band is 5.4 +/- 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/"