[vsnet-grb-info 15681] GRB 141028A: Fermi-LAT detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  16969
SUBJECT: GRB 141028A: Fermi-LAT detection
DATE:    14/10/28 17:34:43 GMT
FROM:    Elisabetta Bissaldi at U.Innsbruk/IAPP  <Elisabetta.Bissaldi at uibk.ac.at>

E. Bissaldi (University & INFN Trieste), J. L. Racusin (NASA/GSFC),
F. Longo (University & INFN Trieste), D. Kocevski (NASA/GSFC),
G. Vianello (Stanford Univ.) and M. Arimoto (Tokyo Tech)
report on behalf of the Fermi-LAT team:

At 10:54:46.78 on October 28, 2014, Fermi-LAT detected high-energy
emission from GRB 141028A, which was also detected by Fermi-GBM
(trigger 436186489/141028455) and initiated an autonomous repoint
of the spacecraft.

The best LAT on-ground location is found to be

RA, Dec  322.70, -0.28 (J2000)

with an error radius of 0.4 deg (90% containment, statistical error only).
This was 25 deg from the LAT boresight at the time of the trigger.
An improved position may be released when additional data is
downlinked from the spacecraft.

The data from the Fermi-LAT show a significant increase in the event
rate at a position consistent with the GBM localization.
More than 20 photons above 100 MeV are observed from trigger
time T0 up to T0+600 s, when the position of the burst moved
out of the LAT FoV.
The highest-energy photon is a 3.9 GeV event which is observed
160 seconds after the GBM trigger.

A Swift ToO has been approved for this burst.

The Fermi-LAT point of contact for this burst is
Makoto Arimoto (arimoto at hp.phys.titech.ac.jp).

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.