Warp and eccentricity propagation in discs around black holes

TL;DR

This paper investigates how warping and eccentric disturbances propagate inward in accretion discs around black holes, highlighting conditions that facilitate this process and its potential link to observed high-frequency QPOs.

Contribution

It applies secular theories to model stationary warp and eccentricity propagation in black hole accretion discs, exploring conditions that enable inward transmission.

Findings

Propagation is enhanced with low viscous damping.

High accretion rates facilitate inward propagation.

Results suggest a link to high-frequency QPOs in black hole systems.

Abstract

We consider the inward propagation of warping and eccentric disturbances in discs around black holes under a wide variety of conditions. In our calculations we use secular theories of warped and eccentric discs and assume the deformations to be stationary and propagating in a disc model similar to regions (a) and (b) of Shakura and Sunyaev discs. We find that the propagation of deformations to the innermost regions of the disc is facilitated for low viscous damping and high accretion rate. We relate our results to the possible excitation of trapped inertial modes, and to the observations of high-frequency quasi-periodic oscillations (QPOs) in black hole systems in the very high spectral state.