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Suárez Juan Carlos, Michel Eric, Houdek Günter, Pérez Hernéndez F., Lebreton Yveline

Mode stability in delta Scuti stars: linear analysis versus observations in open clusters

Monthly notices of the Royal Astronomical Society, 2007, vol. 379, pp. 201-208

Référence DOI : 10.1111/j.1365-2966.2007.11927.x
Référence ADS : 2007MNRAS.379..201S

Résumé :

A comparison between linear-stability analysis and observations of pulsation modes in five delta Scuti stars, belonging to the same cluster, is presented. The study is based on a work by Michel et al., in which such a comparison was performed for a representative set of model solutions obtained independently for each individual star considered. In this paper, we revisit that work by Michel et al. following, however, a new approach which consists of the search for a single, complete, and coherent solution for all the selected stars, in order to constrain and test the assumed physics describing these objects. To do so, refined descriptions for the effects of rotation on the determination of the global stellar parameters and on the adiabatic oscillation frequency computations are used. In addition, a crude attempt is made to study the role of rotation on the prediction of mode instabilities. The present results are found to be comparable with those reported by Michel et al. Within the temperature range log T<SUB>eff</SUB> = 3.87 -3.88, agreement between observations and model computations of unstable modes is restricted to values for the mixing-length parameter alpha<SUB>NL</SUB> ~= 1.50. This indicates that for these stars a smaller value for alpha<SUB>NL</SUB> is required than that suggested from a calibrated solar model. We stress the point that the linear-stability analysis used in this work still assumes stellar models without rotation and that further developments are required for a proper description of the interaction between rotation and pulsation dynamics.

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