Angular momentum transfer by tidally forced oscillations in massive main-sequence stars

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6 Citations (Scopus)

Abstract

We discuss angular momentum transfer by tidally forced oscillations (the dynamical tides) in a massive main-sequence star in a binary system. Because of the periodic gravitational disturbance by the orbital motion of the companion star, low-frequency global oscillations are excited as dynamical tides in the massive main-sequence star We are mainly interested in the case where the orbital motion of the companion star is in resonance with low-order quadruple g-modes of the main-sequence star. Dissipation mechanisms associated with nonaxisymmetric oscillations are known to play essential roles in angular momentum transfer in stars. We show that the deep interior of a massive main-sequence star is a damping (positively dissipative) region and the outer envelope is an excitation (negatively dissipative) region for low-order g-modes. We also show that the tidally forced oscillations whose frequency range overlaps with that of the g-modes have almost the same dissipative (nonadiabatic) properties as the g-modes. It is shown that the rotation of the outer envelope of a massive main-sequence star is driven, by the tidally forced oscillations, in the opposite direction to the orbital motion, as observed in the corotating frame of the main-sequence star. We show that forcing on the outer envelope by a tidal oscillation can be strong enough when the tidal oscillation is in resonance with one of the low-order g-modes of the star. We suggest that tidal oscillations could supply enough angular momentum to support an excretion disk around a Be star (a rapidly rotating massive main-sequence star) in a high-mass X-ray binary system.

Original languageEnglish
Pages (from-to)697-705
Number of pages9
JournalAstrophysical Journal
Volume417
Issue number2
DOIs
Publication statusPublished - 1993 Nov 10
Externally publishedYes

Keywords

  • Binaries: close
  • Stars: early-type
  • Stars: interiors
  • Stars: oscillations

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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