Letter to the Editor

Proper motions and velocity asymmetries in the RW Aur jet ^*

¹ Instituto de Astrofísica de Canarias, c/ Vía Láctea s/n 38200, La Laguna, Tenerife, Spain
² LERMA, Observatoire de Paris, UMR 8112 du CNRS, 61 Av. de l'Observatoire, 75014 Paris, France
³ Laboratoire d'Astrophysique, Observatoire de Grenoble, UMR 5571, BP 53, 38041 Grenoble Cedex 9, France

Corresponding author: L. López-Martín, luislm@ll.iac.es

Received: 4 April 2003
Accepted: 7 May 2003

Abstract

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 °. The inner knot spacing appears best explained by time variability with at least two modes: one irregular and asymmetric (possibly random) on timescales of ≤3–10 yr, and another more regular with 20 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.