Detection of gamma rays above 1 TeV from the Crab Nebula by the second HEGRA imaging atmospheric Cherenkov telescope at La Palma

Abstract The results of observations of the Crab Nebula by the second HEGRA imaging atmospheric Cherenkov telescope during the period 1994/1995 are presented. The signal, detected at a level of 10 σ , allows one to estimate the flux and the spectral index of the γ -ray energy spectrum above 1 TeV. The analysis, based on the comparison of measurements with comprehensive Monte Carlo simulations, reveals a γ -ray flux F γ (≥ 1 TeV) ⋍ 8 × 10 −12 photons cm −2 s −1 , and indicates a rather steep integral spectrum in the energy region 1–3 TeV with a power-law index α ⋍ 1.6–1.8.