[vsnet-grb-info 17348] GRB 151222A: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  18715
SUBJECT: GRB 151222A: Fermi GBM detection
DATE:    15/12/22 17:10:12 GMT
FROM:    Hoi-Fung Yu at MPE  <sptfung at mpe.mpg.de>

Hoi-Fung Yu (MPE) reports on behalf of the Fermi GBM Team:

"At 08:10:13.62 UT on 22 Dec 2015, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 151222A (trigger 472464617 / 151222340).
The on-ground calculated location, using the GBM trigger data, 
is RA = 355, Dec = 36.7 (J2000 degrees, equivalent to 23h 40m, 36d 42'), 
with an uncertainty of 3 degrees (radius, 1-sigma containment, statistical 
only; there is additionally a systematic error which we have characterized 
as a core-plus-tail model, with 90% of GRBs having a 3.7 deg error and 
a small tail suffering a larger than 10 deg systematic error. 
[Connaughton et al. 2015, ApJS, 216, 32] ).

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

The GBM light curve consists of two short pulses with a duration (T90) of 
about 0.8 s (50-300 keV). The time-averaged spectrum from T0-0.256 s 
to T0+0.768 s is best fit by a power law function with an exponential
high-energy cutoff. The power law index is -0.68 +/- 0.09 and
the cutoff energy, parameterized as Epeak, is 1490 +/- 270 keV.

The event fluence (10-1000 keV) in this time interval is
(2.36 +/- 0.13)E-06 erg/cm^2. The 64-ms peak photon flux measured
starting from T0-0.256 s in the 10-1000 keV band
is 12.9 +/- 1.9 ph/s/cm^2.

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