TITLE: GCN CIRCULAR NUMBER: 18065 SUBJECT: GRB 150724B: Fermi-LAT detection DATE: 15/07/25 13:52:53 GMT FROM: Judith Racusin at GSFC E. Bissaldi (INFN Bari), J. L. Racusin (NASA/GSFC), and E. Moretti (MPP Munich) report on behalf of the Fermi-LAT team: At 18:45:36.71 on 2015-07-24, Fermi-LAT detected high-energy emission from GRB 150724B, which was also detected by Fermi-GBM (trigger 459456340/150724782). The best LAT on-ground location is found to be RA, Dec = 351.92, 3.67 (J2000) with an error radius of 0.3 deg (90% containment, systematic error only). This was 58 deg from the LAT boresight at the time of the trigger. The data from the Fermi-LAT show a ~5 sigma increase in the event rate within 7 degrees of the GBM location after the GBM trigger that is spatially and temporally correlated with the GBM emission. More than 11 photons above 100 MeV and 1 photons above 1 GeV were observed within 300 seconds. The highest-energy photon is a 2 GeV event which is observed ~50 seconds after the GBM trigger. A Swift ToO has been requested for this burst. 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.