Tidally driven mean flows in slowly and uniformly rotating massive main sequence stars

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Abstract

We calculate tidally driven mean flows in a slowly and uniformly rotating massive main sequence star in a binary system. We treat the tidal potential due to the companion as a small perturbation to the primary star. We compute tidal responses of the primary as forced linear oscillations, as a function of the tidal forcing frequency ωtide = 2(Ωorb − Ω), where Ωorb is the mean orbital angular velocity and Ω is the angular velocity of rotation of the primary star. The amplitude of the tidal responses is proportional to the parameter f0 ∝ (M2/M)(aorb/R)−3, where M and M2 are the masses of the primary and companion stars, R is the radius of the primary and aorb is the mean orbital separation between the stars. For a given f0, the amplitudes depend on ωtide and become large when ωtide is in resonance with natural frequencies of the star. Using the tidal responses, we calculate axisymmetric mean flows, assuming that the mean flows are non-oscillatory flows driven via non-linear effects of linear tidal responses. We find that the φ-component of the mean flow velocity dominates. We also find that the amplitudes of the mean flows are large only in the surface layers where non-adiabatic effects are significant and that the amplitudes are confined to the equatorial regions of the star. Depending on M2/M and aorb/R, the amplitudes of mean flows at the surface become significant.

Original languageEnglish
JournalUnknown Journal
Publication statusPublished - 2017 Mar 9

Keywords

  • Hydrodynamics
  • Stars: evolution
  • Stars: massive
  • Stars: oscillations
  • Stars: rotation
  • Waves

ASJC Scopus subject areas

  • General

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