GCN Circular 17205

H.-F. Yu (MPE) reports on behalf of the Fermi GBM Team:

"At 06:02:52.49 UT on 20 Dec 2014, the Fermi Gamma-Ray Burst Monitor triggered 
and located GRB 141220A (trigger 141220252/ 141220252), which was also detected
by Swift (Cummings et al. 2014, GCN 17196
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 ). The GBM on-ground location, using 
the Fermi GBM trigger data, is consistent with the Swift location. The trigger 
resulted in an Autonomous Repoint Request (ARR) that was accepted and the 
spacecraft slewed to the GBM in-flight location. The angle from the Fermi LAT 
boresight is about 47 degrees.

The GBM light curve consists of two main pulses with a duration (T90) of about 
7.6 s (50-300 keV). The time-averaged spectrum from T0-1.920 s to T0+8.320 s is
best fit by a power law function with an exponential high-energy cutoff. The 
power law index is -0.80 +/- 0.05 and the cutoff energy, parameterized as Epeak, 
is 180 +/- 9 keV.

The event fluence (8-1000 keV) in this time interval is
(5.23 +/- 0.15)E-06 erg/cm^2. The 1.024-sec peak photon flux measured starting 
from T0+0.128 s in the 8-1000 keV band is 12.0 +/- 0.3 ph/s/cm^2.

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