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Stellar Ages and Convective Cores in Field Main-sequence Stars: First Asteroseismic Application to Two Kepler Targets

V. Silva Aguirre, S. Basu, I. M. Brandão, J. Christensen-Dalsgaard, S. Deheuvels, G. Doǧan, T. S. Metcalfe, A. M. Serenelli, J. Ballot, W. J. Chaplin, M. S. Cunha, A. Weiss, T. Appourchaux, L. Casagrande, S. Cassisi, O. L. Creevey, R. A. García, Y. Lebreton, A. Noels, S. G. Sousa, D. Stello, T. R. White, S. D. Kawaler, H. Kjeldsen

Abstract
Using asteroseismic data and stellar evolution models we obtain the first detection of a convective core in a Kepler field main-sequence star, putting a stringent constraint on the total size of the mixed zone and showing that extra mixing beyond the formal convective boundary exists. In a slightly less massive target the presence of a convective core cannot be conclusively discarded, and thus its remaining main-sequence lifetime is uncertain. Our results reveal that best-fit models found solely by matching individual frequencies of oscillations corrected for surface effects do not always properly reproduce frequency combinations. Moreover, slightly different criteria to define what the best-fit model is can lead to solutions with similar global properties but very different interior structures. We argue that the use of frequency ratios is a more reliable way to obtain accurate stellar parameters, and show that our analysis in field main-sequence stars can yield an overall precision of 1.5%, 4%, and 10% in radius, mass, and age, respectively. We compare our results with those obtained from global oscillation properties, and discuss the possible sources of uncertainties in asteroseismic stellar modeling where further studies are still needed.

Keywords
asteroseismology - stars: fundamental parameters - stars: interiors - stars: oscillations

The Astrophysical Journal
Volume 769, Number 2, Page 141_1
2013 June

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Instituto de Astrofísica e Ciências do Espaço Universidade do Porto Faculdade de Ciências da Universidade de Lisboa Fundação para a Ciência e a Tecnologia
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