3D Models of Radiatively Driven Colliding Winds In Massive O+O Star Binaries: I. Hydrodynamics

TL;DR

This paper uses 3D hydrodynamical models to study the complex wind-wind collision regions in massive O+O star binaries, revealing how cooling, orbital motion, and wind speeds influence the collision dynamics.

Contribution

It introduces detailed 3D hydrodynamical simulations of O+O star binaries, incorporating gravity, wind driving, orbital motion, and radiative cooling, to analyze collision region properties.

Findings

Cooling depends on system separation and orbital phase.

Close systems exhibit rapid cooling due to lower pre-shock wind speeds.

Eccentric systems can retain cold gas at apastron.

Abstract

The dynamics of the wind-wind collision in massive stellar binaries is investigated using three-dimensional hydrodynamical models which incorporate gravity, the driving of the winds, the orbital motion of the stars, and radiative cooling of the shocked plasma. In this first paper we restrict our study to main-sequence O+O binaries. The nature of the wind-wind collision region is highly dependent on the degree of cooling of the shocked plasma, and the ratio of the flow timescale of the shocked plasma to the orbital timescale. The pre-shock wind speeds are lower in close systems as the winds collide prior to their acceleration to terminal speeds. Radiative inhibition may also reduce the pre-shock wind speeds. Together, these effects can lead to rapid cooling of the post-shock gas. Radiative inhibition is less important in wider systems, where the winds are accelerated to higher speeds before they collide, and the resulting collision region can be largely adiabatic. In systems with eccentric orbits, cold gas formed during periastron passage can persist even at apastron, before being ablated and mixed into its surroundings and/or accelerated out of the system.