Arcsecond-Scale X-ray Imaging and Spectroscopy of SS 433 with Chandra HETG

TL;DR

This study uses Chandra HETG data to analyze arcsecond-scale X-ray emission in SS 433, revealing knot-like structures, their ejection history, and the nature of X-ray emission processes, providing insights into jet dynamics and stability.

Contribution

First detailed spatial and spectral analysis of SS 433's arcsecond-scale X-ray emission using extensive Chandra HETG data, linking X-ray knots to jet precession and emission mechanisms.

Findings

X-ray knots are consistent with precession model and ejected ~200 days prior.

X-ray emission extends east-west, comparable to radio emission.

Core X-ray spectrum dominated by thermal plasma, outer regions show non-thermal processes.

Abstract

We present a spatial and spectral analysis of arcsecond-scale X-ray emission in SS 433 using zeroth-order data from Chandra High-Energy Transmission Grating (HETG) observations. The analysis is based on 24 observations acquired between 1999 and 2024, comprising a total exposure of $\sim$850 ks and covering a wide range of orbital and precessional phases. Among these, the $\sim$140 ks observation from 2014 was analyzed in detail for this study. This data provides the best statistics and was taken when the jets were nearly perpendicular to the line of sight and the accretion disk was eclipsed. By applying an energy-dependent subpixel event repositioning algorithm and the Richardson-Lucy deconvolution, we enhanced the spatial resolution and revealed eastern and western knot-like structures at a distance of $\sim$1.7 arcsec ($\sim 10^{17}$ cm) from the core. These features are consistent with the kinematic precession model, and the positions of the knots suggest that they were ejected approximately 200 days prior to the observation. A comparison with VLA radio data obtained at a similar precessional phase shows that the X-ray emission extends east-west on a scale comparable to that of the radio emission. While the core is bright in both X-rays and radio, the brightness contrast between the knots and the core is smaller in X-rays than in radio. Spatially resolved spectroscopy indicates that prominent Fe lines in the core X-ray spectrum are well explained by thermal plasma emission. In contrast, Fe lines are not evident in the outer regions after accounting for potential core contamination, suggesting a dominant contribution from non-thermal processes. These findings imply that the arcsecond-scale X-ray structures may vary observationally with viewing conditions or precessional phase, but likely reflect a relatively stable jet-driving mechanism operating within the SS 433 system.