TITLE:   GCN CIRCULAR
NUMBER:  30219
SUBJECT: GRB 201228B: Fermi GBM observation
DATE:    21/06/12 00:13:12 GMT
FROM:    Cori Fletcher at USRA  <cfletcher@usra.edu>

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/"