Dynamical structure of highly eccentric discs with applications to tidal disruption events

Lynch, Elliot M; Ogilvie, Gordon I.

doi:10.1093/mnras/staa3459

Cited by 16 publications

(6 citation statements)

References 69 publications

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“…The variation of vertical gravity around an eccentric orbit causes the disk to expand in height as it travels from pericenter to apocenter and to collapse on the way back. This "breathing" can have large amplitudes even for mildly eccentric disks (Ogilvie & Barker 2014;Lynch & Ogilvie 2021). For the thickest and most eccentric disks, breathing can even become non-adiabatic: extreme compression can create shocks that eject material vertically (Ryu et al 2021).…”

Section: Effects Of Vertical Gravitymentioning

confidence: 99%

Magnetorotational Instability in Eccentric Disks

Chan

Krolik

Piran

2018

ApJ

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Eccentric disks arise in such astrophysical contexts as tidal disruption events, but it is unknown whether the magnetorotational instability (MRI), which powers accretion in circular disks, operates in eccentric disks as well. We examine the linear evolution of unstratified, incompressible MRI in an eccentric disk orbiting a point mass. We consider vertical modes of wavenumber k on a background flow with uniform eccentricity e and vertical Alfvén speed v A along an orbit with mean motion n. We find two mode families, one with dominant magnetic components, the other with dominant velocity components; the former is unstable at (1 − e) 3 f 2 3, where f ≡ kv A /n, the latter at e 0.8. For f 2 3, MRI behaves much like in circular disks, but the growth per orbit declines slowly with increasing e; for f 2 3, modes grow by parametric amplification, which is resonant for 0 < e 1. MRI growth and the attendant angular momentum and energy transport happen chiefly near pericenter, where orbital shear dominates magnetic tension.

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Section: Effects Of Vertical Gravitymentioning

confidence: 99%

Magnetorotational Instability in Eccentric Disks

Chan

Krolik

Piran

2018

ApJ

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“…However, by incorporating some viscosity prescription and a more general energy equation we might expect that the compressive motions would lead to a significant damping of the warp. Indeed, similar 'nozzle-like' compressive structures occur in eccentric disc models of tidal disruption events (TDEs) wherein bouncing modes are forced periodically as gravity is enhanced at pericenter (Ogilvie & Barker 2014;Lynch & Ogilvie 2020). These motions may release significant amounts of energy as the gas is compressed at closest approach (Zanazzi & Ogilvie 2020;Ryu et al 2021).…”

Section: Discussionmentioning

confidence: 83%

Nonlinear resonant torus oscillations as a model of Keplerian disc warp dynamics

Fairbairn,

Ogilvie

2021

Preprint

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Observations of distorted discs have highlighted the ubiquity of warps in a variety of astrophysical contexts. This has been complemented by theoretical efforts to understand the dynamics of warp evolution. Despite significant efforts to understand the dynamics of warped discs, previous work fails to address arguably the most prevalent regime -nonlinear warps in Keplerian discs for which there is a resonance between the orbital, epicyclic and vertical oscillation frequencies. In this work, we implement a novel nonlinear ring model, developed recently by Fairbairn and Ogilvie, as a framework for understanding such resonant warp dynamics. Here we uncover two distinct nonlinear regimes as the warp amplitude is increased. Initially we find a smooth modulation theory which describes warp evolution in terms of the averaged Lagrangian of the oscillatory vertical motions of the disc. This hints towards the possibility of connecting previous warp theory under a generalised secular framework. Upon the warp amplitude exceeding a critical value, which scales as the square root of the aspect-ratio of our ring, the disc enters into a bouncing regime with extreme vertical compressions twice per orbit. We develop an impulsive theory which predicts special retrograde and prograde precessing warped solutions, which are identified numerically using our full equation set. Such solutions emphasise the essential activation of nonlinear vertical oscillations within the disc and may have important implications for energy and warp dissipation. Future work should search for this behaviour in detailed numerical studies of the internal flow structure of warped discs.

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“…Note the in-phase branches fall below the orbital period whilst the anti-phased solutions are longer than the orbital period. in eccentric disc models of tidal disruption events (TDEs) wherein bouncing modes are forced periodically as gravity is enhanced at pericenter (Ogilvie & Barker 2014;Lynch & Ogilvie 2020). These motions may release significant amounts of energy as the gas is compressed at closest approach (Zanazzi & Ogilvie 2020;Ryu et al 2021).…”

Section: Discussionmentioning

confidence: 99%

Non-linear resonant torus oscillations as a model of Keplerian disc warp dynamics

Fairbairn

Ogilvie

2021

Monthly Notices of the Royal Astronomical Society

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Observations of distorted discs have highlighted the ubiquity of warps in a variety of astrophysical contexts. This has been complemented by theoretical efforts to understand the dynamics of warp evolution. Despite significant efforts to understand the dynamics of warped discs, previous work fails to address arguably the most prevalent regime – nonlinear warps in Keplerian discs for which there is a resonance between the orbital, epicyclic and vertical oscillation frequencies. In this work, we implement a novel nonlinear ring model, developed recently by Fairbairn and Ogilvie, as a framework for understanding such resonant warp dynamics. Here we uncover two distinct nonlinear regimes as the warp amplitude is increased. Initially we find a smooth modulation theory which describes warp evolution in terms of the averaged Lagrangian of the oscillatory vertical motions of the disc. This hints towards the possibility of connecting previous warp theory under a generalised secular framework. Upon the warp amplitude exceeding a critical value, which scales as the square root of the aspect-ratio of our ring, the disc enters into a bouncing regime with extreme vertical compressions twice per orbit. We develop an impulsive theory which predicts special retrograde and prograde precessing warped solutions, which are identified numerically using our full equation set. Such solutions emphasise the essential activation of nonlinear vertical oscillations within the disc and may have important implications for energy and warp dissipation. Future work should search for this behaviour in detailed numerical studies of the internal flow structure of warped discs.

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Dynamical structure of highly eccentric discs with applications to tidal disruption events

Cited by 16 publications

References 69 publications

Magnetorotational Instability in Eccentric Disks

Magnetorotational Instability in Eccentric Disks

Nonlinear resonant torus oscillations as a model of Keplerian disc warp dynamics

Non-linear resonant torus oscillations as a model of Keplerian disc warp dynamics

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