2005/01/24 by Rafal M. Nowakowski, Rafał M. Nowakowski, Nowakowski, Rafal M. · 1 citation
Earth and Planetary Sciences · Physics and Astronomy · #Astro and Planetary Science #Astrophysics (astro-ph) #FOS: Physical sciences #High-pressure geophysics and materials #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0501510
42 pages, 15 figures, to appear in Acta Astronomica
arxiv created 2005/01/24 · openalex publication_date 2005/01/24 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We consider evolution of an unstable acoustic mode interacting with an ensemble of stable g-modes. We show that the static multimode solution does not exist. We then find the condition for the stability of the statistical equilibrium. Performing numerical integration of amplitude equations for a simplified system we find that the acoustic mode amplitude exhibits a large irregular variability on the timescale given by the inverse of the growth rate. The g-mode pairs are excited in significantly wider range of detuning parameters than it is implied by the parametric instability criterion applied to the average amplitude. However, the number of interacting g-mode pairs is reduced because the pairs differing in the detuning parameter by less than their damping rates are synchronized and effectively act as a single pair. We apply the multimode resonant coupling theory to a realistic stellar model. We choose a seismic model of the Delta Scuti star XX Pyxidis. Although for some l=2 modes we find amplitudes of the order of a few milimagnitudes, the typical amplitudes of low-degree modes are much higher. Taking into account the rotational splitting results in decrease of amplitudes by a factor of few which is not enough to obtain consistency with observations. We conclude that in this star and likely in all evolved Delta Scuti stars, the resonant mode coupling cannot be the dominant amplitude limiting effect. The nonresonant saturation of the driving effect must play the role.