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ABRIDGED We present new results on the variations in speed and direction ofthe jet bolides in the Galactic microquasar SS433, from high resolutionspectra, taken with the ESO 3.6-m New Technology Telescope almost nightly over0.4 of a precession cycle. We find: (i) These data exhibit multiple ejectionswithin most 24-hour periods and, throughout the duration of the observingcampaign, the weighted means of the individual bolides, in both the red jet andthe blue jet, clearly exhibit the pronounced nodding known in this system. (ii)We present further evidence for a 13-day periodicity in the jet speed, and showthis cannot be dominated by Doppler shifts from orbital motion. (iii) We showthe phase of this peak jet speed has shifted by a quarter of a cycle in thelast quarter-century. (iv) We show that the two jets ejected by SS433 arehighly symmetric on timescales measured thus far. (v) We demonstrate that theanti-correlation between variations in direction and in speed is not anartifact of an assumption of symmetry. (vi) We show that a recently proposedmechanism (Begelman et al 2006) for varying the ejection speed andanti-correlating it with polar angle variations is ruled out. (vii) The speedof expansion of the plasma bolides in the jets is approximately 0.0024c. Thesenovel data carry a clear signature of speed variations. They have a simple andnatural interpretation in terms of both angular and speed fluctuations whichare identical on average in the two jets. They complement archival optical dataand recent radio imaging.

Fluctuations and symmetry in the speed and direction of the jets of SS433 on different timescales