Eccentric Modes in Disks with Pressure and Self-gravity

Accretion disks around stars, or other central massive bodies, can support long-lived, slowly precessing m = 1 disturbances in which the fluid motion is nearly Keplerian with non-zero eccentricity. We study such "slow modes" in disks that are subject to both pressure and self-gravity force...

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Bibliographic Details
Published in:The Astrophysical journal 2019-02, Vol.872 (2), p.184
Main Authors: Lee, Wing-Kit, Dempsey, Adam M., Lithwick, Yoram
Format: Article
Language:English
Subjects:
Accretion
Accretion disks
accretion, accretion disks
Aspect ratio
Astrophysics
Eccentricity
Fluid motion
Graphical methods
Gravitation
hydrodynamics
Planet formation
Protoplanetary disks
Protoplanets
waves
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Summary:Accretion disks around stars, or other central massive bodies, can support long-lived, slowly precessing m = 1 disturbances in which the fluid motion is nearly Keplerian with non-zero eccentricity. We study such "slow modes" in disks that are subject to both pressure and self-gravity forces. We derive a second-order WKB dispersion relation that describes the dynamics quite accurately and show that the apparently complicated nature of the various modes can be understood in a simple way with the help of a graphical method. We also solve the linearized fluid equations numerically and show that the results agree with the theory. We find that when self-gravity is weak ( , where Q is Toomre's parameter and h is the disk aspect ratio), the modes are pressure-dominated. But when self-gravity is strong ( ), two kinds of gravity-dominated modes appear: one is an aligned elliptical pattern and the other is a one-armed spiral. In the context of protoplanetary disks, we suggest that if the radial eccentricity profile can be measured, it could be used to determine the total disk mass.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/ab010c