Jet production in black-hole X-ray binaries and active galactic nuclei: mass feeding and advection of magnetic fields

TL;DR

This paper explores how magnetic field advection in accretion discs influences jet production in black-hole X-ray binaries and active galactic nuclei, highlighting differences due to disc structure and magnetic flux sources.

Contribution

It proposes a model where geometrically thin discs with magnetic outflows in luminous AGNs enable efficient magnetic field advection, explaining jet presence and absence in different states.

Findings

Magnetic outflows in luminous AGNs facilitate strong magnetic fields near black holes.

Weak magnetic fields in XRBs prevent outflows and jet formation in the thermal state.

Efficient magnetic field advection correlates with jet activity in AGNs.

Abstract

Relativistic jets are observed only in the low/hard and intermediate states of X-ray binaries (XRBs), and are switched off in the thermal state, but they appear to be present in both low-luminosity and luminous active galactic nuclei (AGNs). It is widely believed that strong large-scale magnetic fields is a crucial ingredient in jet production; such fields can be attained only through efficient advection from the outer disc. We suggest that geometrically thin accretion discs with magnetic outflows are present in luminous radio-loud AGNs; this is likely because the interstellar medium provides both mass and sufficient magnetic flux to the outer disc. Most angular momentum of such disc is removed by the outflows, and the radial velocity of the disc is significantly increased compared to viscous drift velocity. This facilitates efficient magnetic field advection through the disc to produce a strong field near the black hole in luminous AGNs, which helps launch relativistic jets. In XRBs, the magnetic fields of the gas from companion stars are too weak to drive outflows from outer discs. Jets are therefore switched off in the thermal state due to inefficient magnetic field advection in the disc.