TITLE:   GCN CIRCULAR
NUMBER:  18736
SUBJECT: GRB 151228A: Fermi GBM observation
DATE:    15/12/28 16:41:59 GMT
FROM:    Peter Veres at UAH  <veresp@gmail.com>

Elisabetta Bissaldi (Politecnico di Bari), Binbin Zhang (UAH) and
Peter Veres (UAH)
report on behalf of the Fermi GBM Team:

"At 03:05:12.46 UT on 28 December 2015, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 151228A (trigger 472964716 / 151228129),
which was also detected by the Swift/BAT
(Ukwatta et al. 2015, GCN 18731).
The GBM on-ground location is consistent with the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 117 degrees.


The GBM light curve consists of a single peak
with a duration (T90) of about 0.26 s (50-300 keV).
The time-averaged spectrum from T0-0.06 s to T0+0.32 s is
well fit by a power law function with an exponential
high-energy cutoff.  The power law index is -0.41 +/- 0.23 and
the cutoff energy, parameterized as Epeak, is 747 +/- 193 keV.

The event fluence (10-1000 keV) in this time interval is
(9.2 +/- 0.8)E-7 erg/cm^2. The 64 ms peak photon flux measured
starting from T0-0.06 s in the 10-1000 keV band
is 12.4 +/- 2.0 ph/s/cm^2.


The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."