Spectral Models of Convection-Dominated Accretion Flows

Abstract

For small values of the dimensionless viscosity parameter, namely $\alpha \lesssim 0.1$, the dynamics of non-radiating accretion flows is dominated by convection; convection strongly suppresses the accretion of matter onto the central object and transports a luminosity $\sim 10^{-3}-10^{-2}\dot{M}{c}^2$ from small to large radii in the flow. A fraction of this convective luminosity is likely to be radiated at large radii via thermal bremsstrahlung emission. We show that this leads to a correlation between the frequency of maximal bremsstrahlung emission and the luminosity of the source, ${\nu }_{\mathrm{peak}}\propto L^{2/3}$. Accreting black holes with X-ray luminosities $10^{-4}{L}_{Edd}\gtrsim L_X(0.5-10\mathrm{keV})\gtrsim 10^{-7}{L}_{Edd}$ are expected to have hard X-ray spectra, with photon indices $\Gamma \sim 2$, and sources with $L_X\lesssim 10^{-9}{L}_{Edd}$ are expected to have soft spectra, with $\Gamma \sim 3.5$. This is testable with {\it Chandra} and {\it XMM}.

final version accepted by ApJ; significant modifications from previous version

References in corpus (9)

• Convection-Dominated Accretion Flows
• Self-Similar Accretion Flows with Convection
• Hydrodynamical Non-radiative Accretion Flows in Two-Dimensions
• Two-dimensional models of hydrodynamical accretion flows into black holes
• Low radiative efficiency accretion in the nuclei of elliptical galaxies
• Hybrid Thermal-Nonthermal Synchrotron Emission from Hot Accretion Flows
• Possible Evidence for Truncated Thin Disks in the Low-Luminosity Active Galactic Nuclei M81 and NGC 4579
• Numerical Simulations of Convective Accretion Flows in Three Dimensions
• The Cooling Flow to Accretion Flow Transition

Cited by in corpus (47)

• The Galactic Center Massive Black Hole and Nuclear Star Cluster
• Chandra X-ray Spectroscopic Imaging of Sgr A* and the Central Parsec of the Galaxy
• Rapid X-ray flaring from the direction of the supermassive black hole at the Galactic Centre
• Accretion Models of Gamma-Ray Bursts
• Completion of a Survey and Detailed Study of Double-Peaked Emission Lines in Radio-Loud AGNs
• Double-Peaked Low-Ionization Emission Lines in Active Galactic Nuclei
• Two Dimensional Adiabatic Flows onto a Black Hole: I. Fluid Accretion
• First Simultaneous NIR/X-ray Detection of a Flare from SgrA*
• Rotating Accretion Flows: From Infinity to the Black Hole
• The Origin of Radio Emission in Low-Luminosity Active Galactic Nuclei: Jets, Accretion Flows, or Both?
• Three-Dimensional Magnetohydrodynamic Simulations of Spherical Accretion
• Further Clues to the Nature of Composite LINER/HII Galaxies
• On the origin of black hole X-ray emission in quiescence: Chandra observations of XTE J1550-564 and H 1743-322
• Polarized NIR and X-ray Flares from SgrA*
• Geometrically Thin Disk Accreting Into a Black Hole
• Spectral Energy Distributions of Weak Active Galactic Nuclei Associated With Low-Ionization Nuclear Emission Regions
• Massive black hole remnants of the first stars in galactic haloes
• Testing Radiatively-Inefficient Accretion Flow Theory: an XMM-Newton Observation of NGC 3998
• X-Ray Observations of XTE J1550-564 During the Decay of the 2000 Outburst - I. Chandra and RXTE Energy Spectra
• Correlated X-ray and Optical Variability in V404 Cyg in Quiescence
• Accretion onto nearby supermassive black holes: Chandra constraints on the dominant cluster galaxy NGC 6166
• On the Radial Structure of Radiatively Inefficient Accretion Flows with Convection
• An Assessment of the Energy Budgets of Low-Ionization Nuclear Emission Regions
• New Analytical Formula for Supercritical Accretion Flows
• The X-ray-faint Emission of the Supermassive Nuclear Black Hole of IC1459
• Modeling mm- to X-ray flare emission from SgrA*
• NUclei of GAlaxies: V. Radio emission in 7 NUGA sources
• The X-ray properties of the black hole transient MAXI J1659-152 in quiescence
• Low density, radiatively inefficient rotating-accretion flow onto a black hole
• X-ray and Radio Variability of M31*, The Andromeda Galaxy Nuclear Supermassive Black Hole
• Halpha Flares from V404 Cyg in Quiescence
• Study of Swift/BAT Selected Low-luminosity Active Galactic Nuclei Observed with Suzaku
• Optical spectroscopy of flares from the black hole X-ray transient A0620-00 in quiescence
• Stellar-Mass Black Holes in the Solar Neighborhood
• ISO investigates the nature of extremely-red hard X-ray sources responsible for the X-ray background
• Spectral properties of Three-dimensional Magneto-hydrodynamical Accretion Flows
• Origin of Radio Emission from Nearby Low-Luminosity Active Galactic Nuclei
• Massive black hole remnants of the first stars II: optical and X-ray signatures in present-day galactic haloes
• Are the jets accelerated from the disk coronas in some active galactic nuclei?
• Compton Heated Outflow from CDAFs
• A search for hyperluminous X-ray sources in the XMM-Newton source catalog
• The S2 star as a probe of the accretion disk of Sgr A*
• The fate of supernova remnants near quiescent supermassive black holes
• Suppression of Gravitational Structure Formation by Cosmological Accretion Heating
• The contribution of young core-collapse supernova remnants to the X-ray emission near quiescent supermassive black holes
• Radio Variability of the Sagittarius ${\mathrm{A}}^{\ast }$ due to an Orbiting Star
• The dependence of the viscosity-parameter on the disk scale height profile