X-ray emission from black-hole binaries

TL;DR

This paper reviews the properties, observational data, and theoretical models of X-ray emission from accreting black holes, focusing on spectral states, variability, and the potential of X-ray polarimetry.

Contribution

It provides a comprehensive overview of current understanding of X-ray emission mechanisms and variability in black-hole binaries, highlighting the diagnostic potential of X-ray polarimetry.

Findings

Correlations between spectral and timing properties are discussed.

X-ray polarimetry offers promising diagnostic insights.

Variability patterns differ across spectral states.

Abstract

The properties of X-ray emission from accreting black holes are reviewed. The contemporary observational picture and current status of theoretical understanding of accretion and formation of X-ray radiation in the vicinity of the compact object are equally in the focus of this chapter. The emphasis is made primarily on common properties and trends rather than on peculiarities of individual objects and details of particular theoretical models. The chapter starts with discussion of the geometry of the accretion flow, spectral components in X-ray emission and black hole spectral states. The prospects and diagnostic potential of X-ray polarimetry are emphasized. Significant attention is paid to the discussion of variability of X-ray emission in general and of different spectral components -- emission of the accretion disk, Comptonized radiation and reflected component. Correlations between spectral and timing characteristics of X-ray emission are reviewed and discussed in the context of theoretical models. Finally, a comparison with accreting neutron stars is made.