Orbital evolution of colliding star and pulsar winds in 2D and 3D: dimensionality, resolution, and grid size effects

V. Bosch-Ramon, M. V. Barkov, M. Perucho

Published 2014-11-28Version 1

The structure formed by the shocked winds of a massive star and a non-accreting pulsar in a binary system suffers periodic and random variations of orbital and non-linear dynamical origin. The characterization of the evolution of the two-wind interaction region is necessary to understand the non-thermal emission from radio to gamma rays. For the first time, we simulate in 3D the interaction of isotropic stellar and relativistic pulsar winds along one full orbit, on scales well beyond the binary size. We also investigate the impact of grid resolution and size. We carry out, with the code PLUTO, relativistic hydrodynamical simulations in 2 and 3D of the interaction of a slow dense wind and a mildly relativistic wind along one full orbit, up to ~100 times the binary size. The 2-dimensional simulations are carried out with equal and larger grid resolution and size than in 3D. The simulations in 3D confirm previous results in 2D, showing a strong shock induced by Coriolis forces that terminates the pulsar wind in all directions, strong bending of the interaction structure against the pulsar motion, and the generation of turbulence. The shocked flows are also subject to a faster development of instabilities in 3D, which enhances the presence of shocks, two-wind mixing, and the disruption of the interaction structure on large scales. In 2D, higher resolution simulations confirm lower resolution results, and simulations with larger grid sizes strengthen the case for the loss of global coherence of the interaction structure. Simulations in 3D confirm that the interaction of stellar and pulsar winds yields structures that evolve non-linearly and get strongly entangled. The evolution is accompanied by strong kinetic energy dissipation, rapid changes in flow orientation and speed, and turbulent motion. The loss of global coherence is strongly enhanced in 3D and as the resolution increases.