DOPPLER-SHIFTED X-RAY-LINE EMISSION FROM SS433

We present the results from a series of X-ray observations of SS433 made with the EXOSA T Observatory in 1983-85 which show that strong iron line emission is present in its X-ray spectrum and displays large energy shifts which vary as a function of the 164-day precession phase. These energy shifts are entirely consistent with the Doppler shifts predicted in the kinematic model for the relativistic jets in SS433. The implication is that the X-ray emitting material is physically associated with the jets. The line energy in the rest-frame is 6.7 keV, suggesting a thermal origin for the line emission. Changes in the visibility of the lines which occur as function of 164-day phase are interpreted as being due to obscuration by a precessing accretion disc. We use this new result to provide additional constraints on the system geometry, and the physical conditions in the jets, and to derive a lower limit to the mass outflow rate. We also discuss the implications for the jet acceleration mechanism. © Royal Astronomical Society.