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 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@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.