ON THE SEPARATION OF THE FLARING COMPONENTS EMISSION IN VARIABLE COMPACT EXTRAGALACTIC RADIO-SOURCES - RESULTS FROM A SIMPLE SHOCKED RELATIVISTIC JET MODEL

Variable compact radio sources are frequently explained as resulting from shocks propagating in otherwise steady relativistic jets. In order to properly interpret flares in the sources it is necessary to correctly separate the emission by the shock structures from the steady flow. It is emphasized in this paper that within these models the background emission is necessarily time-dependent and, during a flare, is not equal to the quiescent phase emission. This behavior is simply due to the replacement of parts of the unshocked flow by the shocked plasma. The importance of this point is illustrated through a simple shocked-jet model. The model has three new features which have not been included in earlier models viz. time delay effects across the flow, a truly arbitrary viewing angle and differences in relativistic electron spectral index between the shocked and unshocked flows.