Modelling the components of binaries in the Hyades: the dependence of the mixing-length parameter on stellar mass


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Yildiz M. , YAKUT K. , BAKIS H., NOELS A.

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, vol.368, no.4, pp.1941-1948, 2006 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 368 Issue: 4
  • Publication Date: 2006
  • Doi Number: 10.1111/j.1365-2966.2006.10275.x
  • Title of Journal : MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
  • Page Numbers: pp.1941-1948
  • Keywords: stars : abundances, binaries : eclipsing, stars : evolution, stars : interiors, open clusters and associations : individual : Hyades, ECLIPSING BINARY, LUMINOSITY-RELATION, MAIN-SEQUENCE, HIPPARCOS PARALLAXES, EVOLUTIONARY MODELS, OXYGEN ABUNDANCES, THETA(2) TAURI, OPEN CLUSTERS, O-I, STARS

Abstract

We present our findings based on a detailed analysis of the binaries of the Hyades, in which the masses of the components are well known. We fit the models of the components of a binary system to observations so as to give the observed total V and B-V of that system and the observed slope of the main sequence in the corresponding parts. According to our findings, there is a very definite relationship between the mixing-length parameter and the stellar mass. The fitting formula for this relationship can be given as alpha = 9.19 (M/M-circle dot-0.74)(0.053)-6.65, which is valid for stellar masses greater than 0.77 M-circle dot. While no strict information is gathered for the chemical composition of the cluster, as a result of degeneracy in the colour-magnitude diagram, by adopting Z = 0.033 and using models for the components of 70 Tau and theta(2) Tau we find the hydrogen abundance to be X = 0.676 and the age to be 670 Myr. If we assume that Z = 0.024, then X = 0.718 and the age is 720 Myr. Our findings concerning the mixing-length parameter are valid for both sets of the solution. For both components of the active binary system V818 Tau, the differences between radii of the models with Z = 0.024 and the observed radii are only about 4 per cent. More generally, the effective temperatures of the models of low-mass stars in the binary systems studied are in good agreement with those determined by spectroscopic methods.