THE PRECESSING JET IN 3C-279

A model of a precessing jet obtained from radio data was used to expla in the optical light curve of the OW quasar 3C 279. The geometrical pa rameters of the model and the bulk motion of the jet were obtained fro m the position angles, velocities, and epoch of formation of the super luminal features in the radio jet. As a consequence, the model provide s 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 w avelengths could be the result of beaming, as the jet approaches its m inimum separation to the line of sight. Fast variability observed at t hese epochs would be naturally explained by the shortening of the time scale in the observer's reference frame due to relativistic effects. T he precessing jet model could also explain the variability in the gamm a-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.