MULTIWAVELENGTH VARIABILITY OF THE SYNCHROTRON SELF-COMPTON MODEL FOR BLAZAR EMISSION

摘要

Motivated by recent reports of strongly correlated radio and X-ray variability in 3C 279 (Grandi et al.), we have computed the relative amplitudes of variations in the synchrotron flux at v and the self-Compton X-ray flux at 1 keV [R(v)] for a homogeneous sphere of relativistic electrons orbiting in a tangled magnetic field. We consider three cases: the Thomson depth of the sphere (τ_T) varying at fixed magnetic field strength (B), B varying at fixed τ_T, and equal fractional changes in τ_T and B. Relative to synchrotron self-Compton scattering without induced Compton scattering, stimulated scattering reduces the amplitude of R(v) by as much as an order of magnitude when τ_T approx> 1. When τ_T varies in a fixed magnetic field, R_τ increases monotonically from 0.01 at v_0, the self-absorption turnover frequency, to 0.5 at 100v_0. Variations in B reduce R at all v, up to a factor of 2 if τ_T is constant, and introduce local extrema in R. The relative amplitudes of the correlated fluctuations in the radio-millimeter and X-ray fluxes from 3C 279 are consistent with the synchrotron self-Compton model if τ_T varies in a fixed magnetic field and induced Compton scattering is the dominant source of radio opacity. The variation amplitudes are too small to be produced by the passage of a shock through the synchrotron emission region unless the magnetic field is perpendicular to the shock front.