TITLE: GCN CIRCULAR NUMBER: 15399 SUBJECT: GRB 131029A: Fermi-LAT detection of a burst DATE: 13/10/30 10:15:12 GMT FROM: Judith Racusin at GSFC J. L. Racusin (NASA/GSFC), G. Vianello (Stanford), Elisabetta Bissaldi (University & INFN Trieste), Rachele Desiante (University of Udine and INFN Trieste), Francesco Longo (University and INFN Trieste), report on behalf of the Fermi-LAT team: Starting around 23:20:48.58 on October 29, 2013 Fermi LAT detected high energy emission from GRB 131029A, which was also detected by Fermi-GBM (trigger 404781651/131029973). The best LAT on-ground location is found to be RA, DEC 200.785, 48.298 (J2000) with an error radius of 0.26 deg (68% containment, statistical error only), this was 60 deg from the LAT boresight at the time of the trigger (i.e., close to the limit of the LAT field of view). This position is ~6 deg away from the best available GBM position, well within the error radius if we include a typical systematic error of 3 deg. The burst position was observed by the LAT from the trigger until ~T0+800 s. The data from the Fermi LAT show a significant increase in the event rate within 10 degree of the GBM location after the GBM trigger that is spatially and temporally correlated with the GBM emission with high significance. More than 19 photons above 100 MeV and more than 3 photons above 1 GeV are observed within 800 seconds. The highest energy photon is a 1.3 GeV event which is observed 70 seconds after the GBM trigger. A Swift ToO has been requested for this burst. The Fermi LAT point of contact for this burst is Judith Racusin (judith.racusin@nasa.gov). 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.