On the interaction of microquasar jets with stellar winds

TL;DR

This study uses 2D simulations to explore how microquasar jets interact with stellar winds, revealing shock formation, particle acceleration potential, and conditions for jet stability or disruption.

Contribution

It provides the first detailed dynamical and radiative analysis of jet-wind interactions in high-mass microquasars using numerical simulations.

Findings

Jets can generate strong shocks in stellar winds.

Particles can be accelerated up to TeV energies in these shocks.

Jets are stable but can be disrupted by wind ram pressure at low powers.

Abstract

Strong interactions between jets and stellar winds at binary system spatial scales could occur in high-mass microquasars. We study here, mainly from a dynamical but also a radiative point of view, the collision between a dense stellar wind and a mildly relativistic hydrodynamical jet of supersonic nature.}{We have performed numerical 2-dimensional simulations of jets, with cylindrical and planar (slab) symmetry, crossing the stellar wind material. From the results of the simulations, we derive estimates of the particle acceleration efficiency, using first order Fermi acceleration theory, and give some insight on the possible radiative outcomes. We find that, during jet launching, the jet head generates a strong shock in the wind. During and after this process, strong recollimation shocks can occur due to the initial overpressure of the jet with its environment. The conditions in all these shocks are convenient to accelerate particles up to $\sim$ TeV energies, which can lead to leptonic (synchrotron and inverse Compton) and hadronic (proton-proton) radiation. In principle, the cylindrical jet simulations show that the jet is stable, and can escape from the system even for relatively low power. However, when accounting for the wind ram pressure, the jet can be bent and disrupted for power $\la 10^{36}$ erg s$^{-1}$.