TITLE: GCN CIRCULAR NUMBER: 44983 SUBJECT: GRB 260618B: Fermi-LAT detection DATE: 26/06/18 22:53:02 GMT FROM: Rahul Gupta at NASA GSFC <rahul.gupta@nasa.gov> R. Gupta (NASA/GSFC), A. Holzmann Airasca (UniTrento and INFN Bari), and N. Di Lalla (Stanford University) report on behalf of the Fermi-LAT collaboration: At 16:55:04.71 UT on June 18th, 2026, Fermi-LAT detected high-energy emission from GRB 260618B, which was also detected by Fermi-GBM (trigger 803494509/260618705, GCN #44979). The best LAT on-ground location is found to be RA, Dec = 354.35, -44.88 (J2000) with an error radius of 0.10 deg (90 % containment, statistical error only). This was 16 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 high significance. The photon flux above 100 MeV in the time interval 0 - 100 s after the GBM trigger is (1.99 ± 0.56)E-5 ph/cm2/s. The estimated photon index above 100 MeV is -1.82 ± 0.21. The highest energy photon has an energy of 6.7 GeV and occurs at 1.8 s after trigger time. The Fermi-LAT point of contact for this burst is Samantha López (lopez@llr.in2p3.fr). 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/44983. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...