On an excitation mechanism for trapped inertial waves in discs around black holes

Abstract

According to one model, high-frequency quasi-periodic oscillations (QPOs) can be identified with inertial waves, trapped in the inner regions of accretion discs around black holes due to relativistic effects. In order to be detected, their amplitudes need to reach large enough values via some excitation mechanism. We work out in detail a non-linear coupling mechanism suggested by Kato, in which a global warping or eccentricity of the disc has a fundamental role. These large-scale deformations combine with trapped modes to generate `intermediate' waves of negative energy that are damped as they approach either their corotation resonance or the inner edge of the disc, resulting in amplification of the trapped waves. We determine the growth rates of the inertial modes, as well as their dependence on the spin of the black hole and the properties of the disc. Our results indicate that this coupling mechanism can provide an efficient excitation of trapped inertial waves, provided the global deformations reach the inner part of the disc with non-negligible amplitude.

15 pages, 7 figures, accepted for publication in MNRAS

References in corpus (3)

• X-ray Properties of Black-Hole Binaries
• Global General Relativistic MHD Simulation of a Tilted Black-Hole Accretion Disk
• The dynamics of eccentric accretion discs in superhump systems

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• Corotational Instability, Magnetic Resonances and Global Inertial-Acoustic Oscillations in Magnetized Black-Hole Accretion Discs
• Warp and eccentricity propagation in discs around black holes
• Hamiltonian hydrodynamics of eccentric discs
• HFQPOs and discoseismic mode excitation in eccentric, relativistic discs. II. Magnetohydrodynamic simulations
• On the formation of a quasi-stationary twisted disc after a tidal disruption event
• X-ray Quasi-Periodic Oscillations in Active Galactic Nuclei and Their Implications for the Changing Look Phenomenon
• Orbital Motion in Spacetimes Influenced by the Presence of Scalar and Electromagnetic Fields