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Asteroseismic estimate of helium abundance of a solar analog binary system

K. Verma, J. P. S. Faria, H. M. Antia, S. Basu, A. Mazumdar, M. J. P. F. G. Monteiro, T. Appourchaux, W. J. Chaplin, R. A. García, T. S. Metcalfe

Abstract
16 CygA and B are among the brightest stars observed by Kepler. What makes these stars more interesting is that they are solar analogs. 16CygA and B exhibit solar-like oscillations. In this work we use oscillation frequencies obtained using 2.5 yr of Kepler data to determine the current helium abundance of these stars. For this we use the fact that the helium ionization zone leaves a signature on the oscillation frequencies and that this signature can be calibrated to determine the helium abundance of that layer. By calibrating the signature of the helium ionization zone against models of known helium abundance, the helium abundance in the envelope of 16 CygA is found to lie in the range of 0.231 to 0.251 and that of 16 CygB lies in the range of 0.218 to 0.266.

Keywords
stars: abundances – stars: individual (HD 186408, HD 186427) – stars: interiors – stars: oscillations – stars: solar-type

The Astrophysical Journal
Volume 730, Number 2, Page 138_1
2014 August

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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 COMPETE 2020 PORTUGAL 2020 União Europeia