X-Ray Emission from Black-Hole Binaries

Abstract

Summary. 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.

Fast Variability from Black-Hole Binaries

“…Finally, in the LHS the variability at high energies is observed to lag that at lower frequencies (see e.g. Nowak et al 1999), consistent with a Comptonization origin for the emission (Gilfanov 2010).…”

“…For a full description of the energy spectra that characterise the LHS and HSS see Gilfanov (2010). In the LHS, the X-ray emission is very noisy, with fractional rms values as high as 40-50%.…”

Accretion Disks and Coronae in the X-Ray Flashlight

“…However, during hard states the X-ray spectra are not consistent with the thermal disk solution; these are instead dominated by a power-law emission component with a high-energy cutoff (e.g. Sunyaev et al 1991;Tanaka and Shibazaki 1996;Ibragimov et al 2005;Gilfanov 2010). This hard emission is typically ascribed to a corona (see Sect.…”

“…Different from an optically thick but geometrically thin accretion disk that produces the observed thermal X-ray emission in LMXBs, the powerlaw hard X-ray emission is believed to be produced from an optically thin but geometrically thick structure near the NS or BH, and is commonly called a corona (e.g. Sunyaev et al 1991;Tanaka and Shibazaki 1996;Ibragimov et al 2005;Gilfanov 2010). However, the formation and exact geometry of the corona is much less understood than that of the disk.…”

Spectral analysis of theXMM–Newtondata of GX 339–4 in the low/hard state: disc truncation and reflection

“…Furthermore, a substantial part of the accreted matter may form an outflow (Blandford & Begelman 1999). Irrespective of the detail, the outer cold disc in this scenario is expected to be truncated (Done et al 2007;Gilfanov 2010;Yuan & Narayan 2014). The truncation is also required in early stages of an outburst, given that the disc in quiescence does not extend down to the ISCO (Lasota, Narayan & Yi 1996).…”