General-relativistic model of hot accretion flows with global Compton cooling

Abstract

We present a model of optically thin, two-temperature, accretion flows using an exact Monte Carlo treatment of global Comptonization, with seed photons from synchrotron and bremsstrahlung emission, as well as with a fully general relativistic description of both the radiative and hydrodynamic processes. We consider accretion rates for which the luminosities of the flows are between ~0.001 and 0.01 of the Eddington luminosity. The black hole spin parameter strongly affects the flow structure within the innermost 10 gravitational radii. The resulting large difference between the Coulomb heating in models with a non-rotating and a rapidly rotating black hole is, however, outweighed by a strong contribution of compression work, much less dependent on spin. The consequent reduction of effects related to the value of the black spin is more significant at smaller accretion rates. For a non-rotating black hole, the compressive heating of electrons dominates over their Coulomb heating, and results in an approximately constant radiative efficiency of approximately 0.4 per cent in the considered range of luminosities. For a rapidly rotating black hole, the Coulomb heating dominates, the radiative efficiency is ~1 per cent and it slightly increases (but less significantly than estimated in some previous works) with increasing accretion rate. We find an agreement between our model, in which the synchrotron emission is the main source of seed photons, and observations of black-hole binaries in their hard states and AGNs at low luminosities. In particular, our model predicts a hardening of the X-ray spectrum with increasing luminosity, as indeed observed below ~0.01 of the Eddington luminosity in both black-hole binaries and AGNs. Also, our model approximately reproduces the luminosity and the slope of the X-ray emission in Cen A.

13 pages, MNRAS, accepted

References in corpus (17)

• Modelling the behaviour of accretion flows in X-ray binaries
• Advection-Dominated Accretion and the Black Hole Event Horizon
• The hard X-ray spectral evolution in X-ray binaries and its application to constrain the black hole mass of ultraluminous X-ray sources
• The accretion mechanism in low-power radio galaxies
• Resolving the innermost parsec of Centaurus A at mid-infrared wavelengths
• Revisiting the "Fundamental Plane" of Black Hole Activity at Extremely Low Luminosities
• Chandra and XMM-Newton Observations of the Nucleus of Centaurus A
• Study of LINER sources with broad H(alpha) emission. X-ray properties and comparision to luminous AGN and X-ray binaries
• On the origin of X-ray emission in some FR Is: ADAF or jet?
• Evidence for a change in the X-ray radiation mechanism in the hard state of Galactic black holes
• A self-consistent hybrid Comptonization model for broad-band spectra of accreting supermassive black holes
• The Suzaku Observation of the Nucleus of the Radio-Loud Active Galaxy Centaurus A: Constraints on Abundances of the Accreting Material
• The Hard X-ray Emission of Cen A
• Twelve and a Half Years of Observations of Centaurus A with RXTE
• Accretion Disk Spectra of the Brightest Ultra-luminous X-ray Source in M82
• Global Compton heating and cooling in hot accretion flows
• Observational evidence for AGNs feedback at parsec scale

Cited by in corpus (19)

• The Radiative Efficiency of Hot Accretion Flows
• Correlation between the photon index and X-ray luminosity of black hole X-ray binaries and active galactic nuclei: observations and interpretation
• Hot accretion flow in black hole binaries: a link connecting X-rays to the infrared
• Modelling spectral and timing properties of accreting black holes: the hybrid hot flow paradigm
• Two-Temperature GRRMHD Simulations of M87
• Polarization constraints on the X-ray corona in Seyfert Galaxies: MCG-05-23-16
• Hot accretion flow with radiative cooling: state transitions in black hole X-ray binaries
• Radiative Properties of Magnetically-Arrested Disks
• Gamma-ray activity of Seyfert galaxies and constraints on hot accretion flows
• Very fast X-ray spectral variability in Cygnus X-1: Origin of the hard and soft-state emission components
• Gamma-ray emission from proton-proton interactions in hot accretion flows
• X-ray spectra of hot accretion flows
• Jet Signatures in the Spectra of Accreting Black Holes
• Observational Signatures of Mass-Loading in Jets Launched by Rotating Black Holes
• On the role and origin of nonthermal electrons in hot accretion flows
• Effects of Spin on High-Energy Radiation from Accreting Black Holes
• The X-ray variation of M81* resolved by Chandra and NuSTAR
• Improved model of X-ray emission from hot accretion flows
• Hot accretion flows in low-luminosity active galactic nuclei in NGC 4258 and NGC 7213