The Origin of Radio Emission in Black Hole X-ray Binaries

TL;DR

This paper investigates the origins of radio emission in black hole X-ray binaries by analyzing accretion-jet dynamics, revealing different efficiencies for thin disks and hot flows, and discussing the role of black hole spin in jet power.

Contribution

It provides a detailed analysis of how accretion disk types and black hole spin influence jet efficiency and radio emission, offering explanations for observed luminosity relations.

Findings

Jet efficiency increases rapidly in high accretion regimes for thin disks.

Hot accretion flows can explain the standard radio/X-ray luminosity track.

Black hole spin may contribute to jet power in the MAD state.

Abstract

We studied the relation of accretion-jet power and disk luminosity, especially the jet efficiencies and disk radiative efficiencies for different accretion disks as well as black hole (BH) spin, in order to explore the origin of radio emission in black hole X-ray binaries (BHXBs). We found that jet efficiency increases more rapidly (efficient) than the nearly constant disk radiative efficiency for thin disk component in high accretion regime, which could account for the steep track ($\mu>1$) in the observed radio and X-ray luminosity relations ($L_{\rm R}\propto L_{\rm X}^{\mu}$), but the thin disk component may not be able to explain the standard track ($\mu\approx 0.6$) in the BHXBs. For hot accretion flows (HAF), the resulting jet efficiency changes along with the large range of accretions from quiescent state to nearly Eddington state, which could account for the standard track in the BHXBs. The BH spin-jet is discussed for the magnetic arrested disk (MAD) state; in this state, the spin-jet power might contribute to a linear correlation between jet power and mass accretion rate for a given source. More accurate observations are required to test the results.