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GCN Circular 15640

GRB 131231A: Fermi-LAT detection of a burst
2013-12-31T18:38:00Z (10 years ago)
Eda Sonbas at NASA/GSFC <>
E. Sonbas (Adiyaman Univ.), J. L. Racusin (NASA/GSFC), D. Kocevski
(NASA/GSFC) and J. McEnery (NASA/GSFC), report on behalf of the Fermi-LAT

At 04:45:16.08 on Dec 31, 2013, Fermi LAT detected high energy emission
from GRB 131231A, which was also detected by Fermi-GBM (trigger

The best LAT on-ground location is found to be RA, Dec 10.585,
-1.845 (J2000) with an error radius of 0.149 deg (90% containment,
statistical error only), this was 40 deg from the LAT boresight at the time
of the trigger.  The GRB was detected at high enough peak flux in the GBM
detectors to trigger an autonomous repoint of the spacecraft, which kept
the source in the LAT field of view for 900 seconds.

The data from the Fermi LAT are temporally correlated with the GBM emission
with high significance.  More than 37 photons above 100 MeV and more than
11 photons above 1 GeV are observed within 900 seconds. The highest energy
photon is a 9.7 GeV event which is observed at 700 seconds after the GBM

A Swift ToO request has been submitted.

The Fermi LAT point of contact for this burst is Eda Sonbas (

The Fermi LAT is a pair conversion telescope designed to cover the energy
band from 20 MeV to greater than 300 GeV. It is the product of an
international collaboration between NASA and DOE in the U.S. and many
scientific institutions across France, Italy, Japan and Sweden.
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