TITLE:   GCN CIRCULAR
NUMBER:  22045
SUBJECT: GRB 171022A: Fermi-LAT detection
DATE:    17/10/23 15:27:39 GMT
FROM:    Elisabetta Bissaldi at U.Innsbruk/IAPP  <Elisabetta.Bissaldi@uibk.ac.at>

M. Palatiello (Univ & INFN Trieste), E. Bissaldi (Poiltecnico & INFN Bari),
M. Axelsson (Stockholm Univ.), M. Yassine (Univ & INFN Trieste),
S. Buson  (NASA/GSFC) and J. Racusin (NASA/GSFC)
report on behalf of the Fermi-LAT team:


On September 22, 2017, Fermi-LAT detected high-energy emission from GRB 171022A,
which was also detected by Fermi-GBM (trigger 530399665) at 21:14:20.77 UTC.

The best LAT on-ground location is found to be

RA, Dec 204.28, 10.98 (degrees, J2000),

with an error radius of 0.16 deg (90% containment, statistical error only).
This position was outside the LAT FoV at the time of the GBM trigger,
and entered the FoV at ~T0+3000s.

The Fermi-LAT data show a significant increase
in the event rate within 12 degrees of the GBM location.
More than 20 photons above 100 MeV are observed between
T0+3000 s and T0+6000 s. The highest-energy photon is a 14 GeV event
which is observed ~4600 seconds after the GBM trigger.

A Swift ToO will not be performed for this GRB due to Sun constraints.

The Fermi-LAT point of contact for this burst is
Michele Palatiello (michele.palatiello@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.