Long-lived Eccentricities in Accretion Disks

Wing Kit Lee, Adam M. Dempsey, Yoram Lithwick

Research output: Contribution to journalArticle

Abstract

Accretion disks can be eccentric: they support m = 1 modes that are global and slowly precessing. But whether the modes remain trapped in the disk - and hence are long-lived - depends on conditions at the outer edge of the disk. Here we show that in disks with realistic boundaries, in which the surface density drops rapidly beyond a given radius, eccentric modes are trapped and hence can live for as long as the viscous time. We focus on pressure-only disks around a central mass, and show how this result can be understood with the help of a simple second-order WKB theory. We show that the longest-lived mode is the zero-node mode in which all of the disk's elliptical streamlines are aligned, and that this mode decays coherently on the viscous timescale of the disk. Hence, such a mode, once excited, could live as long as the lifetime of the disk. It may be responsible for asymmetries seen in recent images of protoplanetary disks.

Original languageEnglish (US)
Article numberL11
JournalAstrophysical Journal Letters
Volume882
Issue number1
DOIs
StatePublished - Sep 1 2019

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ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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