Doppler-shifted X-ray line emission from SS 433.

Abstract

The authors present the results from a series of X-ray observations of SS433 made with the EXOSAT Observatory in 1983 - 1985 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 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. The authors 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. They also discuss the implications for the jet acceleration mechanism.