The active galactic nucleus BL Lac was observed with the Gt-48 atmospheric Cherenkov detector of the Crimean Astrophysical Observatory from July 23-September 1, 1998, in order to search for ultrahigh-energy gamma-ray (>1 TeV) emission. The object was in the field of view of the detector for more than 24 hours. The source was detected with a high level of confidence (7.2 sigma), with a flux equal to (2.1+/-0.4)x10^{ -11} photons cm^{ -2}s^{ -1}.
Categories: astro-ph