A revised dynamical model for SS433 and the nature of the system

We adopt a fundamentally different approach to providing a dynamical description of the strange binary system SS433. Instead of relying solely upon the equations of motion of rigid bodies to obtain constraints on some of the parameters of the system, we make plausible physical assumptions concerning the nature of the system that allow the direct calculation of these parameters. Specifically, we assume that the free-body precession period is the same as the driven precession period, and we assume that the axial rotation period of the precessing object is tidally locked with its orbiting companion. These assumptions are fully consistent with earlier solutions of the full dynamical model, but provide a simpler set of constraints on the model, and yield a completely coherent picture of the components of this binary system. The free parameters of the model are the five physical parameters of the kinematic model plus the five parameters required to describe the 6-d nodding motion. The requirement that the precession results from Newtonian-driven precession then determines the oblateness of the precessing object and the mass ratio of the object to the total mass in the system. We also examine the impact of the discrete behaviour of the jet-bullets on the ability of any continuous model to fit the data, and re-examine the evidence for the location of the mean emitting region of the jets. This is followed by an analysis of the other possible periodicities in the system, particularly the 800-1000-d period suggested by some authors. We conclude that the precessional period of the system varies chaotically, possibly reflecting episodic mass transfer from the companion. Finally, we discuss what these results imply concerning the nature, origin and future of this unique system.