Black Holes in Binary Systems: Observational Appearances

Abstract

The outward transfer of angular momentum of accreting matter can lead to the formation of a disk around the black hole. The structure and radiation spectrum of the disk depends, in the main, on the rate of matter inflow Ṁ into the disk at its external boundary. Dependence on the efficiency of mechanisms of angular momentum transport (connected with the magnetic field and turbulence) is weaker. If Ṁ = 10−9–3 × 10−8 M⊙/yr, the disk around the black hole is a powerful source of X-radiation with hv ∼ 1–10 keV and luminosity L ∼ 1037–1038 erg s−1. If the flux of the accreting matter decreases, the effective temperature of radiation and the luminosity will drop. At the same time when Ṁ > 10−9M⊙ yr−1, the optical luminosity of the disk exceeds the solar one. The main contribution to the optical luminosity of the black hole is due to the re-radiation of that part of the X-ray and ultraviolet energy which is initially produced in the central high temperature regions of the disk and which is then absorbed by the low temperature outer regions. The optical radiation spectrum of such objects must be saturated by the broad emission recombination and resonance lines. Variability is connected with the character of the motion of the black hole and the gas flow in binary systems and possibly with eclipses. For well defined conditions, the hard radiation can evaporate the gas. This can counteract the matter inflow into the disk and lead to autoregulation of the accretion.If M ≫ 3 × 10−8 (M/M⊙) M⊙ yr−1, the luminosity of the disk around the black hole is stabilized at the critical level of Lcr = 1038 (M/M⊙) erg s−1. A small fraction of the accreting matter falls under the gravitational radius whereas the major part of it flows out with high velocities from the central regions of the disk. The outflowing matter is opaque to the disk radiation and completely transforms its spectrum. As a consequence, a black hole in a supercritical regime of accretion can appear as a bright star with a strong outflow of matter.

The power of relativistic jets is larger than the luminosity of their accretion disks

“…These are produced by the superposition of several, larger, components. The emission produced by the accretion disk is assumed to be a multicolor blackbody, with a temperature distribution dictated by the balance of heat production and radiative dissipation 26 . The corresponding values of L disk found through disk fitting are listed in the Extended Data Table 1.…”

“…The uncertainties associated to this method are large (dispersion of σ=0.5 dex for the black hole mass values 25 ), but if there is no systematic error (see Methods) the average Eddington ratio for FSRQs is reliable: Figure 2). This implies that all FSRQ should have standard, geometrically thin, optically thick, accretion disks 26 . Therefore the more powerful jets (the ones associated to FSRQs) can be produced by standard disks with presumably no central funnel, contrary to some expectations 27,28 .…”

The role of viscosity in AGN outflows in relation to jet periodicities

“…According to the Shakura-Sunyaev turbulent viscosity prescription (Shakura 1972;Shakura & Sunyaev 1973), we adopted:…”

Constraints on direct acceleration of UHECRs in astrophysical sources

“…1 presents the predicted cosmic-ray fluxes in the best-fit model for the Auger spectrum [25] for different dependencies of the magnetic field B 0 on SMBH mass mentioned in previous section. Thered curves correspond to B 0 given by the Eddington limit, the green one describes the Shakura-Syunyaev model [17,18] and the blue one corresponds to the model of Ref. [19].…”