SPECTRAL VARIABILITY IN PKS-0528-RAY ENERGIES(134 AT GAMMA)

We present model calculations to the observed spectral variability in the gamma-ray spectrum of the ultraluminous blazar-type quasar PKS 052 8+134. We argue that the observed appearance of a spectral break betwe en the COMPTEL and the EGRET energy range can plausibly be explained b y a variation of the Doppler beaming factor in the framework of a rela tivistic jet model for AGNs, combining the ERC and the SSC model. This may be an instructive example for the different dependence of these t wo spectral components on the Doppler factor, as predicted in earlier work.