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GCN Circular 14102

GRB 121225B: Fermi GBM observation
2012-12-25T18:11:28Z (11 years ago)
Michael S. Briggs at UAH and MSFC <>
D. Tierney (UCD) reports on behalf of the Fermi GBM Team:

"At 10:00:53.58 UT on 25 December 2012, the Fermi Gamma-Ray Burst
Monitor triggered and located GRB 121225B (trigger 378122456 /
121225417). This GRB was also detected by the Fermi LAT (GCN 14101,
Kocevski et al.)

The on-ground calculated location, using the GBM trigger data, is RA =
310.45, DEC = -34.83 (J2000 degrees, equivalent to 20 h 41 m, -34 d 49'),
with an uncertainty of 1.5 degrees (radius, 1-sigma containment,
statistical only; there is additionally a systematic error which is
currently estimated to be 2 to 3 degrees).

The angle from the Fermi LAT boresight is 66 degrees.

The GBM light curve has a multi-pulse time history with with the main
emission complexes at 15 to 25 seconds and at 45 to 65 seconds.  The
duration (T90) is 58.5 +/- 0.8 s (50-300 keV).  The time-averaged
spectrum from T0-1.8 s to T0+73.0 s is best fit by a Band function
with Epeak = 277.6 (+13.1/-12.4) keV, alpha = -1.08 (+0.02/-0.02), and
beta = -2.14 (+0.05/-0.06).

The event fluence (10-1000 keV) in this time interval is (7.16 +/-
0.07)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from
T0+22.0 s in the 10-1000 keV band is 23.6 +/- 0.4 ph/s/cm^2.

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