Two-dimensional studies of inertial-acoustic oscillations in black hole accretion discs

John A. Milsom*, Ronald E Taam

*Corresponding author for this work

Research output: Contribution to journalArticle

21 Scopus citations

Abstract

Radiation hydrodynamic simulations of two-dimensional, optically thick, black hole accretion discs are performed under conditions of varying mass accretion rate, Ṁ/ṀEdd, and kinematic viscosity, ν. Specifically, the effects of inertial-acoustic oscillations and convection on disc structure and observable properties are studied. It is found that global oscillations with rms amplitudes of ≲0.3 per cent can be present at the maximum epicyclic frequency in the disc. These oscillations are favoured for low accretion rates (Ṁ≲ṀEdd) and large viscosities. Local oscillations at the local epicyclic frequencies are always present with rms amplitudes of ≲0.2 per cent. These oscillations yield power spectra with spectral slopes of 0.98 and 1.33. Qualitatively similar behaviour is found for discs described by an alpha law or a constant v. Oscillations may be present for a restricted range of parameters for any viscosity law in which the shear viscosity (μ = ρν) increases upon compression, and they may be detectable with the X-ray Timing Explorer. It is also found that for Ṁ≳0.1ṀEdd convection dominates the transfer of energy in the disc. The convection cells generally stretch from the mid-plane to the disc surface at low accretion rates (Ṁ≲ṀEdd), while the cells appear on varying length-scales at high accretion rates (Ṁ≳ṀEdd).

Original languageEnglish (US)
Pages (from-to)358-368
Number of pages11
JournalMonthly Notices of the Royal Astronomical Society
Volume286
Issue number2
DOIs
StatePublished - Jan 1 1997

Keywords

  • Accretion, accretion discs
  • Black hole physics
  • Convection
  • Hydrodynamics
  • Instabilities
  • Waves

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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