Formation and evolution of transient jets and their cavities in black-hole X-ray binaries

TL;DR

This paper presents a model explaining the origin and evolution of transient jets and their cavities in black-hole X-ray binaries, emphasizing the transition from collimated jets to un-collimated outflows and cavity formation.

Contribution

It introduces a novel model linking jet transitions to accretion rate changes and cavity formation, explaining observed jet behaviors and deceleration mechanisms.

Findings

Transient jets result from transitions in jet collimation due to accretion rate changes.

Cavities formed by uncollimated outflows have low inertia, affecting jet deceleration.

Presence of clouds/filaments can cause modest jet deceleration within cavities.

Abstract

We propose a model explaining the origin of transient/episodic jets in black-hole X-ray binaries, in which they are caused by transitions from a collimated, strongly magnetized, jet to a wide, un-collimated, outflow. The change occurs when the accretion flow leaves the magnetically-choked state due to an increase of the accretion rate for a weakly varying magnetic flux. The formed powerful jet then detaches from its base, and propagates as a discrete ejection. The uncollimated outflow then produces a relativistic plasma that fills surrounding of the black hole, contributing to the formation of a low-density cavity. While the pressure in the cavity is in equilibrium with the surrounding interstellar medium (ISM), its inertia is orders of magnitude lower than that of the ISM. This implies that the plasma cannot efficiently decelerate the ejecta, explaining most of the observations. The modest deceleration within the cavities observed in some cases can be then due to the presence of clouds and/or filaments, forming a wide transition zone between the cavity and the ISM.