Evolution of relativistic jets from XTE J1550-564 and the environment of microquasars

TL;DR

This paper models the evolution of relativistic jets from XTE J1550-564 using an external shock model, revealing environmental asymmetries and proposing a classification of microquasar jets based on surrounding medium properties.

Contribution

It introduces a detailed external shock model for jet evolution, highlighting environmental asymmetries and proposing a new classification framework for microquasar jets.

Findings

Cavity radii of ~0.36 and ~0.46 pc on east and west sides.

Asymmetrical ISM densities of ~0.015 and ~0.21 cm$^{-3}$.

Microquasar environments are generally low-density regions.

Abstract

Two relativistic X-ray jets have been detected with the Chandra X-ray observatory in the black hole X-ray transient XTE J1550-564. We report a full analysis of the evolution of the two jets with a gamma-ray burst external shock model. A plausible scenario suggests a cavity outside the central source and the jets first travelled with constant velocity and then are slowed down by the interactions between the jets and the interstellar medium (ISM). The best fitted radius of the cavity is ~0.36 pc on the eastern side and ~0.46 pc on the western side, and the densities also show asymmetry, of ~0.015 cm$^{-3}$ on the east to ~0.21 cm$^{-3}$ on the west. Large scale low density region is also found in another microquasar system, H 1743-322. These results are consistent with previous suggestions that the environment of microquasars should be rather vacuous, compared to the normal Galactic environment. A generic scenario for microquasar jets is proposed, classifying the observed jets into three main categories, with different jet morphologies (and sizes) corresponding to different scales of vacuous environments surrounding them.