On the uncertain nature of the core of α Cen A

M. Bazot, J. Christensen-Dalsgaard, L. Gizon, O. Benomar

Research output: Contribution to journalArticlepeer-review

Abstract

High-quality astrometric, spectroscopic, interferometric and, importantly, asteroseismic observations are available for α Cen A, which is the closest binary star system to earth. Taking all these constraints into account, we study the internal structure of the star by means of theoretical modelling. Using the Aarhus STellar Evolution Code (astec) and the tools of Computational Bayesian Statistics, in particular a Markov chain Monte Carlo algorithm, we perform statistical inferences for the physical characteristics of the star. We find that α Cen A has a probability of approximately 40 per cent of having a convective core. This probability drops to few per cent if one considers reduced rates for the 14N(p,γ)15O reaction. These convective cores have fractional radii less than 8 per cent when overshoot is neglected. Including overshooting also leads to the possibility of a convective core mostly sustained by the ppII chain energy output. We finally show that roughly 30 per cent of the stellar models describing α Cen A are in the subgiant regime.

Original languageEnglish (US)
Pages (from-to)1254-1269
Number of pages16
JournalMonthly Notices of the Royal Astronomical Society
Volume460
Issue number2
DOIs
StatePublished - 2016

Keywords

  • Convection
  • Stars: evolution
  • Stars: individual: α Cen A
  • Stars: interiors
  • Stars: oscillations
  • methods: statistical

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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