The SS433 jet from subparsec to parsec scales

Context. Relativistic jets associated with compact objects, as in the X-ray binary SS433, are known to be multiscale because they spawn over many orders of magnitude in distance, Here we model the precessing SS433 jet and study its dynamics from O(0.01) to 0(1) parsec scales. Aims. We aim to solve the discrepancy between the observations on a 0.1 pc scale of SS433, where the jet is clearly precessing with an angle of 20 degrees. and the larger scale observations where the jet of SS433 interacts with the associated supernova remnant W50. requiring a precessing angle of 10 degrees. Methods. We use 3D special relativistic hydrodynamical simulations on a domain of a scale of 1 pc. We use the finite volume code MPI-AMRVAC, solving the relativistic variant of the Euler equations. To cover lengthscale variations from O(0.001) pc as the jet beam width up to the domain size, we take full advantage of code parallelization and its adaptive mesh refinement scheme, Results. We found that by means of a simple hydrodynamical process, the jet of SS433 can transit from a precessing jet with an angle of 20, to a continuous hollow non-precessing jet with a smaller opening angle of about 10, Successive windings of the precessing jet helix undergo gradual deceleration by ISM interaction, to ultimately merge in a hollow straight jet at distances where the ram pressure of individual jet elements match the ISM pressure at about 0.068 pc from the source. Conclusions. We solve the discrepancy with an elegant and simple model that does not require the jet of SS433 to undergo any temporal changes in jet injection dynamics, but does so as a consequence of a hydrodynamically enforced spatial recollimation. Our simulation thus serves to validate simpler model prescriptions for SS433 on large scales, where a continuous jet profile suffices.