TITLE: GCN CIRCULAR NUMBER: 22980 SUBJECT: GRB 180720B : Fermi-LAT detection DATE: 18/07/20 22:28:56 GMT FROM: Elisabetta Bissaldi at INFN,Bari E. Bissaldi (Politecnico & INFN Bari) and J. L. Racusin (NASA/GSFC) report on behalf of the Fermi-LAT team: "At 14:21:44.55 UT on July 20, 2018, Fermi-LAT detected high-energy emission from GRB 180720B, which was also detected by Swift (Siegel et al. 2018, GCN 22973) and by Fermi-GBM (trigger 553789304 / 180720598). The best LAT on-ground location is found to be RA, Dec = 0.58, -2.95 (J2000) with an error radius of 0.11 deg (90 % containment, statistical error only). This was 50 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 trigger with very high significance. The highest-energy photon is a 5 GeV event which is observed 137 seconds after the GBM trigger. Given that GRB 180720B is detected by both Swift and Fermi, and it is very bright in the LAT, we encourage follow-up observations. The Fermi-LAT point of contact for this burst is Elisabetta Bissaldi (elisabetta.bissaldi@ba.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."