[vsnet-grb-info 15930] GRB 141222A: Fermi-LAT detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  17218
SUBJECT: GRB 141222A: Fermi-LAT detection
DATE:    14/12/22 17:22:49 GMT
FROM:    Julie McEnery at NASA/GSFC  <julie.e.mcenery at nasa.gov>

J. McEnery (GSFC), D. Kocevski (GSFC), J. Racusin (GSFC), F. Longo 
(University of Trieste and INFN), E.Bissaldi (University of Trieste and 
INFN), and M. Axelsson (KTH Royal Institute of Technology) report on 
behalf of the Fermi-LAT team:

At  07:09:04 UT Mon on Month 22, 2014, Fermi-LAT detected high-energy 
emission from GRB 141222A,
which was also detected by Fermi-GBM (trigger 440924940/141222298).

The best LAT on-ground location is found to be RA, Dec 178.04, -57.35 
(J2000) with an error radius of 0.1 deg (90% containment, statistical 
error only) based on a 500s integration. This was 46 deg from the LAT 
boresight at the time of the trigger.

The data from the Fermi-LAT show a significant increase in the event 
rate within 15 degree of the GBM location after the GBM trigger that is 
spatially and temporally correlated with the GBM emission with high 
significance. More than 5 photons above 100 MeV and more than 1 photon 
above 1 GeV are observed within 1 seconds. The highest-energy prompt 
photon is a 20 GeV event which is observed 0.1 seconds after the GBM 
trigger.

The Fermi-LAT point of contact for this burst is Magnus Axelsson 
(magnusa at astro.su.se <mailto:magnusa at astro.su.se>).

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.