TITLE: GCN CIRCULAR NUMBER: 43850 SUBJECT: GRB 260226A: Fermi-LAT refined analysis DATE: 26/02/26 16:15:30 GMT FROM: Davide Depalo at Politecnico and INFN Bari <davide.depalo@ba.infn.it> D. Depalo (Politecnico and INFN Bari), E. Bissaldi (Politecnico and INFN Bari), A. Holzmann Airasca (UniTrento and INFN Bari), R. Gupta (NASA/GSFC), F. Longo (University and INFN, Trieste), S. Lopez (CNRS / IN2P3), R. Martinelli (University and INFN, Trieste), and J. L. Racusin (NASA/GSFC) report on behalf of the Fermi-LAT team: At 10:38:18.84 UT on Feb 26th, 2026 Fermi-LAT triggered and detected high-energy emission from GRB 260226A (Depalo et al., GCN Circular 43844), which was also detected by Fermi-GBM (trigger 793795080 / 260226443, GCN Circular 43840) and Astrosat (Harsha et al., GCN Circular 43846). The best LAT on-ground location is found to be RA, Dec = 41.93, 7.73 (J2000) with an error radius of 0.11 deg (90 % containment, statistical error only). This was 26 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 - 1.5 ks after the GBM trigger is (1.50 ± 0.06)E-4 ph/cm2/s. The estimated photon index above 100 MeV is -3.25 ± 0.08. The highest energy photon has an energy of 1.1 GeV and occurs at 420 s after trigger time. The Fermi-LAT point of contact for this burst is Niccolò Di Lalla (niccolo.dilalla@stanford.edu). 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/43850. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...