GCN Circular 30219
C. Fletcher (USRA) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 15:21:45.97 UT on 28 December 2020, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 201228B (trigger 630861710 / 201228640) which was also detected by the Swift/BAT-GUANO (DeLaunay et al. 2021, GCN 29985) The Fermi GBM Final Real-time Localization (GCN 29188) is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 39 degrees. The GBM light curve consists of single peak with a duration (T90) of about 30 s (50-300 keV). The time-averaged spectrum from T0-1.5 to T0+30.2 s is best fit by a Band function with Epeak = 49 +/- 14 keV, alpha = 0.8 +/- 1.2, and beta = -1.9 +/- 0.1. The event fluence (10-1000 keV) in this time interval is (2.199 +/- 0.251)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+1.8 s in the 10-1000 keV band is 1.3 +/- 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/"