A 3D dynamical model of the colliding winds in binary systems

TL;DR

This paper introduces a computationally efficient 3D dynamical model for the wind-wind collision regions in binary star systems, capturing the spiral structure and enabling multi-wavelength observational predictions.

Contribution

The model provides a novel, less computationally intensive approach to simulate wind interactions in eccentric binary systems, including the formation of spiral structures.

Findings

Reproduces spiral structures similar to observed pinwheel nebulae

Allows simulation of X-ray emission and absorption in binary systems

Applicable to a range of wavelengths from radio to Gamma-ray

Abstract

We present a 3D dynamical model of the orbital induced curvature of the wind-wind collision region in binary star systems. Momentum balance equations are used to determine the position and shape of the contact discontinuity between the stars, while further downstream the gas is assumed to behave ballistically. An archimedean spiral structure is formed by the motion of the stars, with clear resemblance to high resolution images of the so-called ``pinwheel nebulae''. A key advantage of this approach over grid or smoothed particle hydrodynamic models is its significantly reduced computational cost, while it also allows the study of the structure obtained in an eccentric orbit. The model is relevant to symbiotic systems and Gamma-ray binaries, as well as systems with O-type and Wolf-Rayet stars. As an example application, we simulate the X-ray emission from hypothetical O+O and WR+O star binaries, and describe a method of ray tracing through the 3D spiral structure to account for absorption by the circumstellar material in the system. Such calculations may be easily adapted to study observations at wavelengths ranging from the radio to Gamma-ray.