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Paper: Towards an Observational Validation of the Evolved Theory of Oscillations in Rapidly Rotating Stars
Volume: 479, Progress in Physics of the Sun and Stars
Page: 143
Authors: Böhm, T.
Abstract: The impact of rapid stellar rotation on the evolution of stars is certainly important, but not well understood. In a recent work, an innovative theoretical approach was presented, using tools developed in quantum chaos theory, to calculate oscillation modes of rapidly rotating stars. The results are significantly different from those predicted by the asymptotic theory, which is applicable to slowly rotating stars. In order to validate this new theory we searched for oscillations in the rapidly rotating and pole-on A0-star Vega. While periodic radial velocity variations have been identified with a very low amplitude level in more than 4500 ESPADONS/CFHT and NARVAL/TBL spectra, the confirmation and possible clear attribution to a stellar origin is under investigation; this is based on an analysis of a further 2500 high resolution échelle spectra obtained with the ultra-stable spectrograph SOPHIE/OHP. In a preliminary analysis, clear indications of activity tracing rotational modulation are found in this new data set, as well as higher frequency variations attributed to stellar pulsations. From a theoretical perspective, only the equatorial zones of Vega are cold enough for a kappa-type excitation mechanism to occur, and perhaps only episodically; it is therefore important to extend this study to strong pulsators. Systematic asteroseismic observations and analyses of rapid rotators amongst δ-Scuti stars are proposed, and could be performed with ESPADONS/CFHT, and also highly stabilized instruments such as HARPS/ESO or SOPHIE/OHP. As a first step, asteroseismic observations of one pulsating rapid rotator could allow the validation of the new theoretical framework.
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