Observations of 54 Active Galactic Nuclei with the HEGRA system of Cherenkov telescopes

Abstract

A sample of 54 selected Active Galactic Nuclei (AGN) has been observed with the HEGRA stereoscopic system of Cherenkov Telescopes between 1996 and 2002 in the TeV energy regime. The observations were motivated by the positive results obtained for Mkn 421 and Mkn 501. The distances of the selected objects vary over a large range of redshifts between z = 0.004 and z = 0.7. Among the observed AGN are the now-established TeV-emitting BL Lac type objects H 1426+428 and 1ES 1959+650. Furthermore the BL Lac object 1ES 2344+514 and the radio galaxy M 87 show evidence for a signal on a 4σ level. The observation of 1ES 2344+514 together with the Whipple results firmly establishes this AGN as a TeV source. Several objects (PKS 2155-304, BL Lacertae, 3C 066A) that have been claimed as TeV γ-ray emitters by other groups are included in this data sample but could not be confirmed using data analysed here. The upper limits from several AGN included in this analysis are compared with predictions in the frame-work of SSC models.