A unified accretion-ejection paradigm for black hole X-ray binaries

Abstract

Context. It has been suggested that the cycles of activity of X-ray binaries (XRB) are triggered by a switch in the dominant disk torque responsible for accretion. As the disk accretion rate increases, the disk innermost regions therefore change from a jet-emitting disk (JED) to a standard accretion disk (SAD). Aims. While JEDs have been proven to successfully reproduce X-ray binary hard states, the existence of an outer cold SAD introduces an extra nonlocal cooling term. We investigate the thermal structure and associated spectra of such a hybrid disk configuration. Methods. We use a two-temperature plasma code, allowing for outside-in computation of the disk local thermal equilibrium with self-consistent advection and optically thin-to-thick transitions in both radiation and gas supported regimes. The nonlocal inverse Compton cooling introduced by the external soft photons is computed by the BELM code. Results. This additional cooling term has a profound influence on JED solutions, allowing a smooth temperature transition from the outer SAD to the inner JED. We explore the full parameter space in disk accretion rate and transition radius, and show that the whole domain in X-ray luminosities and hardness ratios covered by standard XRB cycles is well reproduced by such hybrid disk configurations. Precisely, a reasonable combination of these parameters allows us to reproduce the 3–200 keV spectra of each of five canonical XRB states. Along with these X-ray signatures, JED-SAD configurations also naturally account for the radio emission whenever it is observed. Conclusions. By varying only the radial transition radius and the accretion rate, hybrid disk configurations combining an inner JED and an outer SAD are able to simultaneously reproduce the X-ray spectral states and radio emission of X-ray binaries during their outburst. Adjusting these two parameters, it is then possible to reproduce a full cycle. This will be shown in a forthcoming paper.

NuSTAR/XMM–Newton monitoring of the Seyfert 1 galaxy HE 1143-1810

“…Within this paradigm, the accretion flow has two constituents: an outer SAD, extending down to a transition radius r J where the magnetization becomes of order unity, and an inner JED down to the innermost stable circular orbit (ISCO). When the transition radius is close to the ISCO, the thermal emission from the SAD dominates and the source is in a soft state; for large transition radii, the X-ray emission from the JED dominates and the source is in a hard state (for details, see Marcel et al 2018a). In addition to the transition radius, the other crucial parameter is the accretion rate, which determines the total luminosity and influences the aspect ratio of the disc height to radius (Marcel et al 2018b).…”

“…In addition to the transition radius, the other crucial parameter is the accretion rate, which determines the total luminosity and influences the aspect ratio of the disc height to radius (Marcel et al 2018b). The evolution of transition radius and accretion rate can explain the spectral properties of X-ray binaries like GX 339-4 during outbursting cycles (Marcel et al 2018a(Marcel et al , 2019.…”

“…∆χ 2 /∆dof = +4/ + 13 compared with the two-corona fit). The electron temperature and Thomson optical depth of the JED are computed as a function of radius assuming thermal equilibrium (Marcel et al 2018a). We obtained a temperature of roughly ∼ 10 8 K and an optical depth of 3-4, i.e.…”

“…The SAD produces multicolour disc black-body spectra, with typical temperatures of ∼ 10 eV, while the inner JED, below ∼ 10 R G , strongly radiates in the hard X-rays. The sum of the different contributions yields a smooth power-law spectrum (see also Marcel et al 2018a). 10 5 10 6 10 7 10 8 10 9…”

Generation and Transport of Magnetic Flux in Accretion–Ejection Flows

“…In doing so, gravitational energy is transformed into the kinetic energy of the outflow, thus there is no need for it to be radiated locally in the disk. This action of the large scale magnetic field suppresses the total radiation from the disk and modifies its high-energy spectrum [5,6,7].The study of accretion flows is very complicated by itself. Now that we have concluded that accretion flows co-exist and as it seems do depend strongly on ejection flows, one needs to study accretion and ejection as one coherent process.…”