TeV Gamma-Rays from 1ES1959+650

TeV gamma-rays from the BL Lac object 1ES1959+650 have been measured during the years 2000 and 2001 with a significance of 5.2{sigma} at a value of 5.3% of the Crab flux and in May 2002 during strong outbursts with >23{sigma} at a flux level of up to 2.2Crab, making 1ES1959+650 the TeV Blazar with the third best event statistics. The deep observation of 197.4h has been performed with the HEGRA stereoscopic system of 5 imaging atmospheric Cherenkov telescopes (IACT system). 1ES1959+650 is located at a redshift of z=0.047, providing an intermediate distance between the nearby Blazars Mkn 421 and Mkn 501, and the much more distant object H1426+428.

This makes 1ES1959+650 an important candidate of the class of TeV Blazars in view of the absorption of TeV photons by the diffuse extragalactic background radiation (DEBRA). The differential energy spectrum of 1ES1959+650 during the flares can be well described by a power law with an exponential cut-off at (4.2(+0.8-0.6)_stat_+/-0.9_sys_) TeV and a spectral index of 1.83+/-0.15_stat_+/-0.08_sys_, while the low state spectrum can be fitted by a pure power law with a spectral index of 3.18+/-0.17_stat_+/-0.08_sys_.