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Nonlinearity of nonradial modes in evolved stars

Rafal M. Nowakowski·Wojciech A. Dziembowski
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Abstract

We show that in evolved stars, even at relatively low surface amplitudes, nonradial modes become strongly nonlinear in the hydrogen shell source, where the Brunt-Vaisala frequency has its absolute maximum. The measure of nonlinearity is the product of horizontal displacement times the radial wavenumber. It becomes large already in evolved delta-Scuti stars. This nonlinearity presents a major problem for interpretations of amplitude modulation in RR Lyrae stars in terms of nonradial mode excitation.

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Rafal M. Nowakowski, Wojciech A. Dziembowski. 2003-01-24. Nonlinearity of nonradial modes in evolved stars. https://arxiv.org/abs/astro-ph/0301504

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