Colliding Stellar Winds Structure and X-ray Emission

TL;DR

This paper analyzes the structure and X-ray emission of colliding stellar winds in massive binaries, providing new analytical formulas and revealing how the shock geometry and X-ray properties depend on wind momentum ratios.

Contribution

It introduces new analytical expressions for shock angles and shocked wind fractions, improving understanding of wind collision dynamics in massive star binaries.

Findings

Contact discontinuity angles are overestimated by existing formulas at low momentum ratios.

Shocks in primary and secondary winds flare by approximately 20 degrees from the contact discontinuity.

X-ray luminosity scales with the wind momentum ratio and spectra soften as the ratio decreases.

Abstract

We investigate the structure and X-ray emission from the colliding stellar winds in massive star binaries. We find that the opening angle of the contact discontinuity (CD) is overestimated by several formulae in the literature at very small values of the wind momentum ratio. We find also that the shocks in the primary (dominant) and secondary winds flare by approx 20 degrees compared to the CD, and that the entire secondary wind is shocked when the wind momentum ratio < 0.02. Analytical expressions for the opening angles of the shocks, and the fraction of each wind that is shocked, are provided. We find that the X-ray luminosity scales with the wind momentum ratio, and that the spectrum softens slightly as the wind momentum ratio decreases.