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GCN Circular 15333

Subject
GRB 131014A: Fermi-LAT detection
Date
2013-10-14T17:23:36Z (11 years ago)
From
Elisabetta Bissaldi at U.Innsbruk/IAPP <Elisabetta.Bissaldi@uibk.ac.at>
R. Desiante (University of Udine and INFN Trieste), D. Kocevski(NASA/Goddard),
G. Vianello (Stanford), F.Longo, E.Bissaldi (University and INFN Trieste)
and E.Troja (NASA/GSFC/CRESST) report on behalf of the Fermi-LAT team:


At 05:09:00.20 on 2013-10-14 Fermi LAT detected high energy emission
from GRB 131014A, which was also detected by Fermi-GBM (G. Fitzpatrick
and S. Xiong, GCN 15332).

The best LAT on-ground location is found to be RA, DEC 100.5, -19.1 (J2000)
with an error radius of 0.45 deg (68% containment, statistical error only).
This was at the edge of the field of view of the LAT at the time of the
trigger (~70 deg away from the instrument axis). The burst triggered an
autonomous repoint of the spacecraft, which moved it well within the LAT
field-of-view for an additional 500s, before the source was occulted
by the Earth.

Due to the large angle at which the burst was observed during most of the
exposure, we expect a systematic error on the position of up to 0.5 deg.
This is due to the fact that the reconstruction of the direction of incoming
photons is biased toward the axis of the instrument for sources at very
large off-axis angles.

More than 7 photons above 100 MeV and 3 photons above 1 GeV are observed
within 100 seconds. The highest energy photon is a 1.8 GeV event which is
observed ~15 seconds after the GBM trigger.
A single peaked emission lasting roughly 5 seconds can be seen using the
non-standard LAT Low Energy (LLE) with a significance of ~23 sigma.

A Swift ToO request for this burst has been submitted and approved.

The Fermi LAT point of contact for this burst is
Rachele Desiante (rachele.desiante@ts.infn.it).

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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