Structure, strength, and polarization changes in radio source SS433

Abstract

VLA observations of SS433 at 1,465, 4,885, and 15,035 MHz between 8 September 1979 and 20 June 1980 show structure with size scales between 0.1 and 5 arc s which changes significantly on time scales of 1–2 weeks. Jets with 8–20% linear polarization are ejected on both sides of the central radio source which is coincident with the optical image, along position angles between 80° and 120° with a mean position angle for ejected material of 100°. Features in linear polarized intensity maps can be identified in four successive epochs spanning 196 days, and the resulting proper motions for identifiable clouds are 0.0088 arc s per day. If the feature velocities are equal to that of the optical emission lines, the distance to SS433 is 5.1 kpc. The position angles of identifiable features correlate well with the known precessing optical jets if one extrapolates back to the time of ejection using the observed transverse speeds. The equipartition magnetic field strengths of 0.001–0.01 G indicate synchrotron lifetimes of 109–1011 s; therefore synchrotron losses are not a dominant factor in the evolution of the extended radio emission. The evolution of radio jets indicates that the relativistic electrons and magnetic fields seen as synchrotron emission may be generated by flows along the rotation axis of the accretion disk of the SS433 star system.