Jet velocity in SS433: its anti-correlation with precession-cone angle   and dependence on orbital phase
  We present a re-analysis of the optical spectroscopic data on SS433 from the last quarter-century and demonstrate that these data alone contain systematic and identifiable deviations from the traditional kinematic model for the jets: variations in speed, which agree with our analysis of recent radio data; in precession-cone angle and in phase. We present a simple technique for separating out the jet speed from the angular properties of the jet axis, assuming only that the jets are symmetric. With this technique, the archival optical data reveal that the variations in jet speed and in precession-cone angle are anti-correlated in the sense that when faster jet bolides are ejected the cone opening angle is smaller. We also find speed oscillations as a function of orbital phase. 
Katherine Blundell & Michael Bowler (Oxford)