Journal Article

Amplitudes of low-frequency modes in rotating B-type stars

Umin Lee

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 420, issue 3, pages 2387-2398
Published in print March 2012 | ISSN: 0035-8711
Published online February 2012 | e-ISSN: 1365-2966 | DOI:
Amplitudes of low-frequency modes in rotating B-type stars

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Using the weakly non-linear theory of oscillation, we estimate the amplitudes of low-frequency modes in a slowly pulsating B star, taking account of the effects of rotation on the modes. Applying the formulation by Schenk et al., we compute the non-linear coupling coefficient between the low-frequency modes and estimate the equilibrium amplitudes of the modes excited in the star, assuming the amplitudes of the unstable modes are saturated as a result of non-linear coupling with stable modes, i.e. as a result of parametric instability expected between one unstable mode and two stable modes. We use the traditional approximation to calculate adiabatic and non-adiabatic oscillations in a rotating star. We find r-modes in a rapidly rotating star play a significant role in the amplitude determination through non-linear coupling. We also find that for low-m modes, the fractional amplitudes of the radiative luminosity caused by the low-frequency modes are of order 10−4 to 10−3 at the surface.

Keywords: instabilities; stars: early-type; stars: oscillations; stars: rotation

Journal Article.  6550 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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