Jets and environment of microquasars

TL;DR

This paper analyzes the evolution of relativistic jets in microquasars using a gamma-ray burst external shock model, revealing environmental asymmetries and proposing a classification based on surrounding medium properties.

Contribution

It introduces a comprehensive model for microquasar jet evolution considering environmental cavities and asymmetries, and proposes a classification scheme based on jet morphology and environment.

Findings

Jets initially travel with constant velocity before slowing down due to ISM interactions.

Asymmetrical cavity sizes and densities are observed around the jets.

Microquasar environments are generally more vacuous than typical Galactic regions.

Abstract

Two relativistic X-ray jets have been detected with the Chandra X-ray observatory from 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 $\sim$0.36 pc on the eastern side and $\sim$0.46 pc on the western side, and the densities also show asymmetry, of $\sim$0.015 cm$^{-3}$ on the east to $\sim$0.21 cm$^{-3}$ on the west. A 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.