The Precessing Jet in 3C 279

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Abstract
A model of a precessing jet obtained from radio data was used to explain the optical light curve of the OVV quasar 3C 279. The geometrical parameters of the model and the bulk motion of the jet were obtained from the position angles, velocities, and epoch of formation of the superluminal features in the radio jet. As a consequence, the model provides the Doppler factor time dependence. This factor reached its maximum value at the epoch in which the very strong and fast optical flare was observed. Therefore, the large increases in the emission at optical wavelengths could be the result of beaming, as the jet approaches its minimum separation to the line of sight. Fast variability observed at these epochs would be naturally explained by the shortening of the timescale in the observer's reference frame due to relativistic effects. The precessing jet model could also explain the variability in the γ-ray emission assuming that the high-energy radiation is produced by the inverse Compton process on external seed photons. The variability would occur when the precessing jet sweeps the broadline region clouds, which would provide the seed photons.