2010MNRAS.401.1983S

The very short time-scale variability of TeV γ-ray emission from active galaxies suggests that the acceleration process of particles and the production of primary γ-rays likely occur relatively close to the accretion disc. We calculate the γ-ray spectra produced in an inverse Compton e^± pair cascade initiated by primary γ-rays which are injected close to the surface of the accretion disc. Possible synchrotron energy losses of secondary cascade e^± pairs are also taken into account. Since the soft radiation field is anisotropic, the resulting γ-ray spectra strongly depend on the observation angle. We investigate their basic properties for different parameters describing such a model. The model is applied to the misaligned blazar Cen A recently detected in the TeV γ-rays. We conclude on the site of the γ-ray emission region in Cen A based on the comparison of the model with the observations of this source in the GeV-TeV energy range.