GCN Circular 29161
J. Wood (NASA/MSFC) reports on behalf of the Fermi GBM Team: "At 17:58:25.69 UT on 23 December 2020, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 201223A (trigger 630439110 / 201223749) which was also detected by the Swift/BAT and Swift/XRT (Gropp et al. 2020, GCN 29158). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 63 degrees. The GBM light curve shows multiple peaks with a duration (T90) of about 33 s (50-300 keV). The time-averaged spectrum from T0-17 s to T0+13 s is best fit by a Band function with Epeak = 86 +/- 12 keV, alpha = 0.14 +/- 0.38 and beta = -2.6 +/- 0.4. A power law function with an exponential high-energy cutoff fits the spectrum equally well. The power law index is -0.14 +/- 0.24 and the cutoff energy, parameterized as Epeak, is 99 +/- 8 keV. The event fluence (10-1000 keV) in this time interval is (2.1 +/- 0.3)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+4.1 s in the 10-1000 keV band is 2.4 +/- 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/"