Chemical composition and the location of the Hyades main sequence in the color-magnitude and mass-luminosity diagrams.
Summary. A method is developed which serves to answer the question how far an observed metal overabundance as measured by the atmospheric parameter [Fe/H] can be explained by lower original hydrogen content, X, or must be traced back to true metal enrichment, Z. Relative displacements of zero-age sequences of stars with changing X and Z in color- magnitude diagrams are calculated with atmospheric blanketing effects taken into account. Comparison with observation in the Hyades case, which is thoroughly rediscussed, yields - for [Fe/H] = +0.3 and Upton's (1971) values for the relative location of unevolved field stars with [Fe/H] =0 - a slight reduction of the original hydrogen content (X =0.6) and a metal enrichment (Z =0.035) as compared to a standard composition (X =0.70, Z = 0;02). With van Altena's distance modulus m - M =3.23, for which the Hyades white dwarfs fit the DA sequence, one obtains the most favorable compromise between all quantities observed. The mass-luminosity discrepancy is considerably reduced. Key words: Hyades - main sequence location - chemical composition - distance
Astronomy and Astrophysics
- Pub Date:
- June 1973