The intermediate-frequency peaked BL Lacertae (IBL) object 3C66A is detected during 2007-2008 in VHE (very high energy; E > 100 GeV) γ rays with the VERITAS stereoscopic array of imaging atmospheric Cherenkov telescopes. An excess of 1791 events is detected, corresponding to a significance of 21.2 standard deviations (σ), in these observations (32.8 hr live time). The observed integral flux above 200 GeV is 6% of the Crab Nebula's flux and shows evidence for variability on the timescale of days. The measured energy spectrum is characterized by a soft power law with photon index Γ = 4.1 0.4stat 0.6sys. The radio galaxy 3C66B is excluded as a possible source of the VHE emission.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science