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Catalogue POP – Notice individuelle de publication

Bossini Diego, Miglio Andrea, Salaris M., Vrard M., Cassisi S., Mosser Benoît, Montalbán Josefina, Girardi Léo, Noels Arlette, Bressan A., Pietrinferni A., Tayar Jamie

Kepler red-clump stars in the field and in open clusters: constraints on core mixing

Monthly notices of the Royal Astronomical Society, 2017, vol. 469, pp. 4718-4725

Référence DOI : 10.1093/mnras/stx1135
Référence ADS : 2017MNRAS.469.4718B

Résumé :

Convective mixing in helium-core-burning (HeCB) stars is one of the outstanding issues in stellar modelling. The precise asteroseismic measurements of gravity-mode period spacing (DeltaPi<SUB>1</SUB>) have opened the door to detailed studies of the near-core structure of such stars, which had not been possible before. Here, we provide stringent tests of various core-mixing scenarios against the largely unbiased population of red-clump stars belonging to the old-open clusters monitored by Kepler, and by coupling the updated precise inference on DeltaPi<SUB>1</SUB> in thousands of field stars with spectroscopic constraints. We find that models with moderate overshooting successfully reproduce the range observed of DeltaPi<SUB>1</SUB> in clusters. In particular, we show that there is no evidence for the need to extend the size of the adiabatically stratified core, at least at the beginning of the HeCB phase. This conclusion is based primarily on ensemble studies of DeltaPi<SUB>1</SUB> as a function of mass and metallicity. While DeltaPi<SUB>1</SUB> shows no appreciable dependence on the mass, we have found a clear dependence of DeltaPi<SUB>1</SUB> on metallicity, which is also supported by predictions from models.

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