Discovery of a Very High Energy Gamma-Ray Signal From the 3c 66a/B Region

The MAGIC telescope observed the region around the distant blazar 3C 66A for 54.2 hr in 2007 August–December. The observations resulted in the discovery of a γ-ray source centered at celestial coordinates R.A. = 2 h 23 m 12 s and decl. = 43°0 7 (MAGIC J0223+430), coinciding with the nearby radio galaxy 3C 66B. A possible association of the excess with the blazar 3C 66A is discussed. The energy spectrum of MAGIC J0223+430 follows a power law with a normalization of (1.7 ± 0.3 stat ± 0.6 syst ) × 10 −11 TeV −1 cm −2 s −1 at 300 GeV and a photon index Γ = −3.10 ± 0.31 stat ± 0.2 syst .