Modelling colliding wind binaries with RAMSES, extension to special relativity

TL;DR

This paper presents high-resolution simulations of colliding stellar winds using RAMSES, incorporating special relativity to study the complex instabilities and structures in gamma-ray and stellar binaries.

Contribution

The authors extend RAMSES with a relativistic hydrodynamics solver and demonstrate its application to modeling colliding wind binaries with detailed instability analysis.

Findings

Kelvin-Helmholtz instability causes mixing and variability.

Non-linear Thin Shell Instability affects the interaction region.

Relativistic simulations reveal differences in flow structure between gamma-ray and stellar binaries.

Abstract

We present high resolution simulations with RAMSES of supersonic colliding stellar winds. The collision results in a double shock structure which is subject to different instabilities. The Kelvin-Helmholtz instability (KHI) introduces some mixing and variability. For isothermal winds, the Non-linear Thin Shell Instability violently affects the interaction region. Properly modelling these instabilities requires a high enough resolution and an adapted numerical method, especially when one of the winds strongly dominates the other one. At large scale, orbital motion is expected to turn the shocked zone into a spiral but we find that in some configurations the KHI may disrupt the spiral. A colliding wind structure is also expected in gamma-ray binaries composed of a massive star and a young pulsar which emits a highly relativistic wind. Numerical simulations are necessary to understand the geometry of such systems and should take into account the relativistic nature of the pulsar wind. We implemented a second order Godunov method to solve the equations of relativistic hydrodynamics with RAMSES, including the possibility for Adaptive Mesh Refinement. After a brief overview of our numerical implementation, we will present preliminary simulation that contrast the structure of the flow in gamma-ray and stellar binaries.