Proper motions and velocity asymmetries in the RW Aur jet

We present adaptive optics spectro-imaging observations of the RW Aur jet in optical forbidden lines, at an angular resolution of 0.4". Comparison with HST data taken 2 years later shows that proper motions in the blueshifted and redshifted lobes are in the same ratio as their radial velocities, a direct proof that the velocity asymmetry in this jet is real and not an emissivity effect. The inferred jet inclination to the line of sight is i = 46 +/- 3degrees. The inner knot spacing appears best explained by time variability with at least two modes: one irregular and asymmetric ( possibly random) on timescales of less than or equal to3-10 yr, and another more regular with similar or equal to20 yr period. We also report indirect evidence for correlated velocity and excitation gradients in the redshifted lobe, possibly related to the blue/red velocity and brightness asymmetry in this system.