TITLE: GCN CIRCULAR NUMBER: 20155 SUBJECT: GRB 161109A: Fermi-LAT detection DATE: 16/11/09 14:56:49 GMT FROM: Elisabetta Bissaldi at U.Innsbruk/IAPP R. Desiante (INFN Torino), E. Bissaldi (Politecnico & INFN Bari), F. Longo (University & INFN Trieste), M. Negro (University and INFN Torino), and J. Racusin (NASA/GSFC) report on behalf of the Fermi-LAT team: At 06:18:45.66 UT on November 09, 2016, Fermi-LAT detected high-energy emission from GRB 161109A, which was also detected by Fermi-GBM (trigger 500365129). The best LAT on-ground location is found to be RA, Dec: 157.86, 61.80 (degrees, J2000) with an error radius of 0.26 deg (90% containment, statistical error only). This was 75 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 that is spatially and temporally correlated with the GBM emission with high significance. More than 60 photons above 100 MeV and about 4 photons above 1 GeV are observed between T0+400 s and T0+1800 s. The highest-energy photon is a 3.5 GeV event which is observed 600 seconds after the GBM trigger. A Swift ToO has been requested for this burst. The Fermi-LAT point of contact for this burst is Francesco Longo (francesco.longo@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.