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

Xiang Liu,Ning Chang,Qi Yuan,Xin Wang

doi:10.3390/galaxies9040078

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 (μ>1) in the observed radio and X-ray luminosity relations (LR∝LXμ), but the thin disk component may not be able to explain the standard track (μ≈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.

Highlights

Among compact binary systems, those that consist of a main sequence or evolved star (S) and compact objects such as a black hole (BH), a neutron star (NS) or a white dwarf (WD) are of special interests
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 the BH spin-jet to explore the origin of radio emission in black hole X-ray binaries (BHXBs)
We find that jet efficiency increases more rapid than the nearly constant disk radiative efficiency for thin disk component in the high accretion regime, which could account for the steep track in the LR –LX plane, but the thin disk component may not be able to explain the standard track in the BHXBs

Summary

Introduction

Those that consist of a main sequence or evolved star (S) and compact objects such as a black hole (BH), a neutron star (NS) or a white dwarf (WD) are of special interests. Electromagnetic emission is often observed in close BH-S, NS-S, and WD-S binaries, when the stellar matter is accreting onto the compact object. For the purpose of understanding the origin of the radio emission, in this paper we investigate the correlation between radio jet and other properties in black hole X-ray binaries (BHXBs). We chose BH systems because there are only two parameters (mass and spin) for a BH, and there is another advantage, i.e., BH has no solid surface (the situation is more complicated for close NS-S, or WD-S binaries due to the strong magnetic field structure and the hard surface of compact object). We will briefly introduce the radio properties of those BHXBs and investigate, from a theoretical point of view, the plausible/sound models for their radio origin

The Radio Emission of BHXB

The Origin of Radio Emission

BH Spin Contribution

Discussion

Findings

Summary and Outlook

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