Pair Cascades and the Gamma Ray Spectra of Active Galactic Nuclei

Our current understanding of the physics of Active Galactic Nuclei AGN suggests that intense optical UV and X ray radiation elds should exist in the central regions of AGN These radiation elds are intense enough that high energy rays propagating through them are likely to pair produce and thus be absorbed before they can escape from the central source region of an AGN If the absorbed rays are su ciently energetic the electron positron pairs created will initiate an electromagnetic pair cascade on the ambient radiation eld We review here the types of emission spectra that can be produced by a pair cascade and discuss their relevance to AGN spectra In particular we examine the possibility that cascades may be occuring in the blazar AGN sources detected by EGRET and are responsible for their observed ray spectra If this is the case we do not expect these AGN to be strong TeV sources and their spectra should show a strong cuto due to intrinsic absorption at energies E GeV