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HFQPOs and discoseismic mode excitation in eccentric, relativistic discs. I. Hydrodynamic simulations.

Published version
Peer-reviewed

Type

Article

Change log

Authors

Dewberry, Janosz W 
Latter, Henrik N 
Ogilvie, Gordon I 
Fromang, Sebastian 

Abstract

High-frequency quasi-periodic oscillations (HFQPOs) observed in the emission of black-hole X-ray binary systems promise insight into strongly curved spacetime. Discoseismic' oscillations with frequencies set by the intrinsic properties of the central black hole, in particular trapped inertial waves' (r-modes), offer an attractive explanation for HFQPOs. To produce an observable signature, however, such oscillations must be excited to sufficiently large amplitudes. Turbulence driven by the magnetorotational instability (MRI) fails to provide the necessary amplification, but r-modes may still be excited via interaction with accretion disc warps or eccentricities. We present 3D global hydrodynamic simulations of relativistic accretion discs, which demonstrate for the first time the excitation of trapped inertial waves by an imposed eccentricity in the flow. While the r-modes' saturated state depends on the vertical boundary conditions used in our unstratified, cylindrical framework, their excitation is unambiguous in all runs with eccentricity >0.005 near the ISCO. These simulations provide a proof of concept, demonstrating the robustness of trapped inertial wave excitation in a non-magnetized context. In a companion paper, we explore the competition between this excitation, and damping by magnetohydrodynamic turbulence.

Description

Keywords

accretion, accretion discs, black hole physics, hydrodynamics, instabilities, waves, X-rays: binaries

Journal Title

Monthly Notices of the Royal Astronomical Society

Conference Name

Journal ISSN

0035-8711
1365-2966

Volume Title

Publisher

Oxford University Press

Rights

All rights reserved
Sponsorship
Science and Technology Facilities Council (ST/P000673/1)