Multi-Wavelength Variability of the Synchrotron Self-Compton Model for Blazar Emission

Abstract

Motivated by recent reports of strongly correlated radio and X-ray variability in 3C279 (Grandi, etal 1995), we have computed the relative amplitudes of variations in the synchrotron flux at $ν$ and the self-Compton X-ray flux at 1 keV ($R(ν)$) for a homogeneous sphere of relativistic electrons orbiting in a tangled magnetic field. Relative to synchrotron self-Compton scattering without induced Compton scattering, stimulated scattering reduces the amplitude of $R(ν)$ by as much as an order of magnitude when $τ_T \gtwid 1$. When $τ_T$ varies in a fixed magnetic field, $R_τ$ increases monotonically from 0.01 at $ν_o$, the self-absorption turnover frequency, to $0.5$ at $100 ν_o$. The relative amplitudes of the correlated fluctuations in the radio-mm and X-ray fluxes from 3C279 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 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.