Colliding-wind Binaries with strong magnetic fields

TL;DR

This paper investigates how strong magnetic fields influence the structure and dynamics of colliding wind binary systems through magnetohydrodynamic simulations, enhancing understanding of particle acceleration and emission processes.

Contribution

It presents detailed MHD simulations of colliding wind binaries with strong magnetic fields, focusing on wind collision region structures and magnetic effects.

Findings

Magnetic fields significantly alter wind collision region morphology.

Strong magnetic fields influence particle acceleration zones.

Simulation results highlight the importance of magnetic effects in emission modeling.

Abstract

The dynamics of colliding wind binary systems and conditions for efficient particle acceleration therein have attracted multiple numerical studies in the recent years. These numerical models seek an explanation of the thermal and non-thermal emission of these systems as seen by observations. In the non-thermal regime, radio and X-ray emission is observed for several of these colliding-wind binaries, while gamma-ray emission has so far only been found in $\eta$ Carinae and possibly in WR 11. Energetic electrons are deemed responsible for a large fraction of the observed high-energy photons in these systems. Only in the gamma-ray regime there might be, depending on the properties of the stars, a significant contribution of emission from neutral pion decay. Thus, studying the emission from colliding-wind binaries requires detailed models of the acceleration and propagation of energetic electrons. This in turn requires a detailed understanding of the magnetic field, which will not only affect the energy losses of the electrons but in case of synchrotron emission also the directional dependence of the emissivity. In this study we investigate magnetohydrodynamic simulations of different colliding wind binary systems with magnetic fields that are strong enough to have a significant effect on the winds. Such strong fields require a detailed treatment of the near-star wind acceleration zone. We show the implementation of such simulations and discuss results that demonstrate the effect of the magnetic field on the structure of the wind collision region.