Iron emission lines from extended, reheated, thermal X-ray jets in SS 433

Abstract

We present a deep Chandra ACIS-S observation of the X-ray binary jet source SS 433. Arcsec-scale X-ray jets are clearly resolved on either side of the core, aligned with the well-known radio jets and the major axis of the associated W50 remnant. We are able to extract X-ray spectra separately for each side of the jet, and find evidence for a hot continuum and Doppler-shifted emission lines. The evidence strongly indicates that material at least half a year downstream in the jet flow from SS 433 is reheating itself to high (>10 7 K) temperatures, presumably by conversion of some fraction of the jets’ enormous kinetic energy. This is the first direct evidence for ongoing heating of thermal plasma downstream in a jet from an X-ray binary system. These observations are seemingly in conflict with all existing models for X-ray and optical line production in the jets of SS 433, in which matter should be cooled down below X-ray-emitting temperatures within, at most, a few hours after being ejected. Possible physical interpretations of these results are briefly discussed.