Beaming and precession in the inner jet of 3 C 273

We have investigated the effects of precession in the inner jet of 3C 273 on its beaming properties and high energy emission. We have used all available VLBI data to determine the kinematic evolution of the jet. The position angles, velocities and formation epochs of different superluminal components are consistent with a precessing inner jet. The time-dependence of the Doppler factor for this jet was computed and the implications for the γ-ray emission are discussed. Additionally, the model, when considered along with simultaneous radio and X-ray variability observations, provides an upper bound to the possible values of the Hubble constant (H0 < 80 km s−1 Mpc−1).