On the interaction of microquasar jets with stellar winds

¹ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, Bonn 53121, Germany e-mail: perucho@mpifr-bonn.mpg.de
² Max Planck Institut für Kernphysik, Saupfercheckweg 1, Heidelberg 69117, Germany e-mail: vbosch@mpi-hd.mpg.de

Received: 26 October 2007
Accepted: 6 February 2008

Abstract

Context. Strong interactions between jets and stellar winds at binary-system, spatial-scales could occur in high-mass microquasars.

Aims. 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.

Methods. We have performed numerical two-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 provide insight into the possible radiative outcomes.

Results. 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 ~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 at relatively low power. However, when accounting for the wind ram pressure, the jet can be bent and disrupted for power 10³⁶ erg s^-1.