TITLE: GCN CIRCULAR NUMBER: 43645 SUBJECT: GRB 260208A: Fermi-LAT detection DATE: 26/02/08 15:21:39 GMT FROM: Davide Depalo at Politecnico and INFN Bari <davide.depalo@ba.infn.it> F. Longo (University and INFN, Trieste), D. Depalo (Politecnico and INFN Bari), A. Holzmann Airasca (UniTrento and INFN Bari) and R. Gupta (NASA/GSFC) report on behalf of the Fermi-LAT team: At 05:07:28.24 UT on February 8th, 2026 Fermi-LAT detected high-energy emission from GRB 260208A, which was also detected by Fermi-GBM (trigger 792220053 / 260208214, GCN #43635), MASTER (GCN #43640) and GOTO (GCN #43641). The best LAT on-ground location is found to be RA, Dec = 204.57, 33.77 (J2000) with an error radius of 0.15 deg (90 % containment, statistical error only). This was 80 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 400 - 2500 s after the GBM trigger is (2.86 ± 0.65)E-6 ph/cm2/s. The estimated photon index above 100 MeV is -1.99 ± 0.19. The highest-energy photon is a 5.3 GeV event which is observed 1168 seconds after the GBM trigger. A Swift ToO request has been approved for this burst. The Fermi-LAT point of contact for this burst is Chiara Bartolini (chiara.bartolini@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. View this GCN Circular online at https://gcn.nasa.gov/circulars/43645. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...