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GCN Circular 23598

Subject
GRB 181231A: Fermi GBM detection
Date
2018-12-31T18:56:12Z (5 years ago)
From
Peter Veres at UAH <veresp@gmail.com>
P. Veres, R. Hamburg and C. Meegan (all UAH)
report on behalf of the Fermi GBM Team:

"At 03:27:43.75 UT on 31 December 2018, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 181231A (trigger 567919668 / 181231144)
which was also detected by Fermi/LAT (Dirirsa et al., GCN 23597).
The GBM on-ground location is consistent with the LAT position.

The GBM light curve shows multiple peaks
with a duration (T90) of about 37 s (50-300 keV).
The time-averaged spectrum from T0-7.2 s to T0+30.7 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -0.63 +/- 0.13 and
the cutoff energy, parameterized as Epeak, is 215 +/- 25 keV.

The event fluence (10-1000 keV) in this time interval is
(6.23 +/- 0.46)E-6 erg/cm^2. The 1 second peak photon flux measured
starting from T0+14.3 s in the 10-1000 keV band
is 2.70 +/- 0.27 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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