Deceleration of SS433 radio jets

TL;DR

This paper investigates the non-dissipative deceleration of SS 433's radio jets caused by interaction with ambient medium, modeling their kinematics and matching observed deviations from ballistic trajectories.

Contribution

It introduces a model explaining jet deceleration and twisting due to ambient medium interaction, fitting observed jet deviations and morphology in SS 433.

Findings

Jets decelerate mostly within the first fifth of precession period.

Model explains observed jet morphology and brightness profiles.

Deceleration accounts for phase deviations and distance measurement discrepancies.

Abstract

The mildly relativistic jets of SS\,433 are believed to inflate the surrounding supernova remnant W\,50 depositing in its expansion possibly more than 99% of their kinetic energy (\cite[1998]{Dub98}). Where and how this transformation of energy is curried out, it is not yet known. What can we learn from it that the jets decelerate and the deceleration is non-dissipative, i.e. radiatively dark. In this paper we unclose the observed deviations of the precessing radio jets of SS\,433, within a few arcseconds from a jets source, from the ballistic track, described by the kinematic model, as a signature of the deceleration which, on other hand, issues from the jets colliding with ambient medium. For that we model kinematics of these colliding jets. The ram pressure on the jets is estimated from the observed profile of brightness of synchrotron radiation along the radio jets. We have found that to fit observed locus the radio jets should be decelerated and twisted, additionally to the precession twist, mostly within the first one-fifth of precession period, and further they extend imitating ballistic jets. The fitted physical parameters of the jet model turned out to be physically reliable and characteristic for SS\,433 jets that unlikely to be occasional. This model explains naturally, and meets approval by a) the observed shock-pressed morphology of the radio jets and their brightness, b) the observed $\sim 10%$ deflections from the standard kinematic model --- just a magnitude of the jet speed decrement in the model, c) regularly observed for the radio jets the precession phase deviation from the standard kinematic model prediction, d) dichotomy of distance to the object, 4.8\,kpc vs. 5.5\,kpc, determined on the basis of the radio jets kinematics on scales of a sub-arcsecond and several arcseconds.