Analysis of accretion disc structure and stability using open code for vertical structure

Abstract

Radial structure of accretion discs around compact objects is often described using analytic approximations which are derived from averaging or integrating vertical structure equations. For non-solar chemical composition, partial ionization, or for supermassive black holes, this approach is not accurate. Additionally, radial extension of `analytically-described' disc zones is not evident in many cases. We calculate vertical structure of accretion discs around compact objects, with and without external irradiation, with radiative and convective energy transport taken into account. For this, we introduce a new open Python code, allowing different equations of state (EoS) and opacity laws, including tabular values. As a result, radial structure and stability `S-curves' are calculated for specific disc parameters and chemical composition. In particular, based on more accurate power-law approximations for opacity in the disc, we supply new analytic formulas for the farthest regions of the hot disc around stellar-mass object. On calculating vertical structure of a self-irradiated disc, we calculate a self-consistent value of the irradiation parameter $C_{\mathrm{irr}}$ for stationary $\alpha$-disc. We find that, for a fixed shape of the X-ray spectrum, $C_{\mathrm{irr}}$ depends weakly on the accretion rate but changes with radius, and the dependence is driven by the conditions in the photosphere and disc opening angle. The hot zone extent depends on the ratio between irradiating and intrinsic flux: corresponding relation for $T_{\mathrm{irr},\mathrm{crit}}$ is obtained.

Accepted for publication in MNRAS, 15 pages, 15 figures, 3 appendix

References in corpus (13)

• The NumPy array: a structure for efficient numerical computation
• Modules for Experiments in Stellar Astrophysics (MESA)
• Modelling the behaviour of accretion flows in X-ray binaries
• Stability of helium accretion discs in ultracompact binaries
• Convection Causes Enhanced Magnetic Turbulence in Accretion Disks in Outburst
• The viscosity parameter alpha and the properties of accretion disc outbursts in close binaries
• Opacity Driven Convection and Variability in Accretion Disks around Supermassive Black Holes
• The thermal-viscous disk instability model in the AGN context
• Modeling of non-stationary accretion disks in X-ray novae A 0620-00 and GRS 1124-68 during outburst
• Impact of convection and resistivity on angular momentum transport in dwarf novae
• An Improved Model for the Spectra of Disks of Nova-like Variables
• Convection in axially symmetric accretion discs with microscopic transport coefficients
• Physical modeling of viscous disc evolution around magnetized neutron star. Aql X-1 2013 outburst decay

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