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Astron. Astrophys. 329, L57-L60 (1998)

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Letter to the Editor

Spectral variability in PKS 0528+134 at gamma-ray energies

M. Böttcher 1 and W. Collmar 2

1 Rice University, Space Physics and Astronomy Department, 6100 S. Main Street, Houston, TX 77005 - 1892, USA
2 Max-Planck-Institut für Extraterrestrische Physik, Postfach 16 03, D-85740 Garching, Germany

Received 25 September 1997 / Accepted 14 October 1997


We present model calculations to the observed spectral variability in the [FORMULA] -ray spectrum of the ultraluminous blazar-type quasar PKS 0528+134. We argue that the observed appearance of a spectral break between the COMPTEL and the EGRET energy range can plausibly be explained by a variation of the Doppler beaming factor in the framework of a relativistic jet model for AGNs, combining the ERC and the SSC model. This may be an instructive example for the different dependence of these two spectral components on the Doppler factor, as predicted in earlier work.

Key words: galaxies: active – quasars: individual – gamma-rays: observations – gamma-rays: theory

Send offprint requests to: M. Böttcher

© European Southern Observatory (ESO) 1998

Online publication: December 16, 1997