The termination region of high-mass microquasar jets

¹ Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2, Ireland
e-mail: valenti@cp.dias.ie; vbosch@mpi-hd.mpg.de
² Dept. d’Astronomia i Astrofísica, Universitat de València, C/ Dr. Moliner 50, 46100 Burjassot (València), Spain
e-mail: Manel.Perucho@uv.es
³ Institut für Astronomie und Astrophysik, Universität Tübingen, Sand 1, 72076 Tübingen, Germany
⁴ INTEGRAL Science Data Centre, Université de Genève, Chemin d’Ecogia 16, 1290 Versoix, Switzerland
e-mail: pol.bordas@uni-tuebingen.de

Received: 20 December 2010
Accepted: 16 January 2011

Abstract

Context. The environment of high-mass X-ray binaries can be characterized either by the supernova remnant that forms these systems or by the wind from the companion massive star. These regions should be tenuous but very hot and surrounded by a dense and cold shocked ISM shell. The interaction between the jet and such a complex medium, also affected by the system proper motion, can lead to very different jet termination structures.

Aims. The evolution of the jet termination regions during the life of a high-mass microquasar is simulated to improve our present understanding of these structures. Also, the evolving emission characteristics are modeled to inform potential observational campaigns of this class of object.

Methods. We performed 2D numerical simulations of jets propagating in different scenarios, corresponding to different epochs after the formation of the high-mass X-ray binary, using the code Ratpenat. We also made simple estimates of the nonthermal emission that could be produced in the jet termination regions.

Results. We find that, in the way through the hot and tenuous medium of the shocked wind/supernova ejecta, the jet suffers recollimation shocks in which it loses part of its thrust and ends in a strong shock inflating a hot cocoon. The jet head propagates with a speed that is similar to the medium sound speed, until it eventually reaches the denser and colder shocked ISM and the unperturbed ISM later on. In these last stages of evolution, the jet is significantly slowed down and can be disrupted. For relatively old sources, the microquasar peculiar velocity becomes important, leading to complete jet destruction. Extended nonthermal radiation can be generated in the jet termination regions, and hard X-rays and TeV photons are the wavelengths best suited for observing these structures.