TITLE:   GCN CIRCULAR
NUMBER:  29206
SUBJECT: GRB 201227A: Fermi GBM observation
DATE:    20/12/30 14:00:33 GMT
FROM:    Rachel Dunwoody at UCD  <rachel.dunwoody@ucdconnect.ie>

S. Lesage, P. Veres, C. Meegan (all UAH), J. Mangan (UCD) and R. Dunwoody
(UCD)
report on behalf of the Fermi GBM Team:

"At 15:14:07.41 UT on 23 December 2020, the Fermi Gamma-Ray Burst Monitor
(GBM)
triggered and located GRB 201227A (trigger 630774852 / 201227635),
which was also detected by Konus-Wind (Svinkin et al. GCN 29196),
Insight-HXMT (Xiao et al., GCN 29187),
AGILE (Ursi et al., GCN 29179) and IPN (Svinkin et al., GCN 29182).
The GBM on-ground location is consistent with the IPN position.



The angle from the Fermi LAT boresight at the GBM trigger time is 135
degrees.



The GBM light curve consists of a short bright pulse
with a duration (T90) of about 0.1 s (50-300 keV).
The time-averaged spectrum from T0-64 ms to T0+128 ms is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -0.47 +/- 0.07 and
the cutoff energy, parameterized as Epeak, is 1076 +/- 96 keV.

The event fluence (10-1000 keV) in this time interval is
(3.6 +/- 0.1)E-6 erg/cm^2. The 64-ms peak photon flux measured
starting from T0 in the 10-1000 keV band
is 100 +/- 5 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/"