Tera-electron-volt radiation from the blazar 1ES 1959+650 in 2004

Observations of the blazar 1ES 1959+650, which has been identified as a point source of tera-electron-volt gamma-ray emission, were carried out on the GT-48 Cherenkov telescope of the Crimean Astrophysical Observatory from the middle of July to the middle of August 2004. Our analysis of data with an effective exposure time on-source of six hours under good weather conditions shows a clear excess of detected photons (with energies E ≥ 1 TeV) in the direction of this source, with a statistical significance of 5.2σ. Using observations of the Crab Nebula in 2002–2004 and the parameters of Cherenkov flashes similar to those observed for 1ES 1959+650 yields an estimated flux for this object of 2.0 ± 0.7 Crab (≥1 TeV). Comparison with the 2–12 keV emission of this source indicates a correlation between the mean fluxes in the two energy ranges in various observing periods.