TITLE:   GCN CIRCULAR
NUMBER:  31210
SUBJECT: GRB 211211A: Fermi GBM observation
DATE:    21/12/12 07:31:36 GMT
FROM:    Joe Mangan at UCD  <joseph.mangan@ucdconnect.ie>

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

At 13:09:59.651 UT on 11 December 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 211211A (trigger 660921004 / 211211549)
which was also detected by the Swift/BAT (D'Ai et al., GCN 31202). The
Fermi GBM Final Real-time Localization (GCN 31201) is consistent with
the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 106.5 degrees.

The GBM light curve consists of an exceptionally bright emission made
up of three separate pulses
with a duration (T90) of about 34.3s (50-300 keV).
The time-averaged spectrum from T0-1.264 s to T0+54.033 s is
best fit by a Band function with Epeak = 646.8 +/- 7.8 keV,
alpha = -1.3 +/- 0.00, and beta = -2.4 +/- 0.02

The event fluence (10-1000 keV) in this time interval is
(5.4 +/- 0.01)E-04 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+6.8 s in the 10-1000 keV band
is 324.9 +/- 1.5 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/