1996A&A...313..759R

Recent observations with the COMPTEL instrument on the Compton Gamma Ray Observatory (CGRO) have revealed that several blazar-type sources present a strong peak in the 0.75-8.0 MeV range of their emission. Moreover, at least four of these objects have displayed variability in the soft γ-ray flux over timescales of months. In this paper I present a model for such variability based on the interaction of a strong relativistic shock with density inhomogeneities in the inner pair beam of these sources. The shock increases the soft γ-emission by compression of the particle density and the consequent enhancement of the blue-shifted annihilation radiation. The shocked particles also emit synchrotron radiation producing simultaneous or quasi-simultaneous outbursts at lower frequencies. This model is applied to the well-studied quasar 3C 273, a source for which multifrequency temporal observations are available.