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GCN Circular 15587

GRB 131209A: Fermi-LAT detection of a burst
2013-12-10T02:06:01Z (11 years ago)
Giacomo Vianello at SLAC <>
G.Vianello (Stanford), N.Omodei (Stanford), report on behalf of the
Fermi-LAT team:

At 13:07:56.97on December 9, 2013, Fermi LAT detected a faint high energy
signal from GRB131209A, which was also detected by Fermi-GBM (trigger

The data from the Fermi LAT show a significant increase in the event rate
within 10 degree of the GBM location after the GBM trigger that is
spatially and temporally correlated with the GBM emission. Although the
detection is slightly above the 5 sigma level, there are only 4 photons
likely associated with this GRB in the first 200 s after the trigger. The
localization has therefore a large statistical error. The best LAT
on-ground location is found to be RA, DEC 136.5, -33.2 (J2000) with an
error radius of 0.9 deg (68% containment, statistical error only), this was
20 deg from the LAT boresight at the time of the trigger.

The Fermi LAT point of contact for this burst is Giacomo Vianello (

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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