Publication Abstracts

Oinas 1974

Oinas, V., 1974: Strong-line K stars. II. Chemical abundances. Astrophys. J. Supp. Series, 27, 405-414, doi:10.1086/190303.

A model-atmosphere analysis has been carried out for 26 K-type giant and dwarf stars, 10 of which have been classified as "super-metal-rich" (SMR) by Spinrad and Taylor and Taylor. The observational data include deblanketed scanner measurements as well as equivalent widths from high-dispersion spectra.

A preliminary rough analysis and the final model-atmosphere approach both yield a temperature-dependent spectroscopic gravity defect; i.e., the metal abundances from neutral and ionized species can be brought into agreement only by forcing the gravities to be unacceptably low as one goes to lower temperatures. Various possible explanations, having to do with errors in the models or in the mode of analysis, are considered, but none is found to be satisfactory. It is suggested that the effect may be caused by a new opacity source that is acting to steepen the spectral gradient in the visual and near-infrared, thereby lowering the apparent temperatures. It is shown that the new opacity also explains various discrepancies noted by other observers.

A comparison of the metal abundances of stars of the same temperature leads to the conclusion that the SMR stars are generally overabundant in the metals by about 0.2-0.3 dex. An overabundance of sodium by about 0.5 dex is found for all the SMR stars, with the exception of the dwarf 54 Psc, which is found to have essentially solar abundances. The iron overabundance is rather marginal in most of the giants (Δ Fe = 0.1) and might not be real.

No correlation is found between metal abundance and turbulence. In particular, the SMR stars in this program are found to possess normal microturbulent velocities. The large ultraviolet deficiencies in the SMR stars can be explained by the effects of a relatively moderate metal enhancement on the colors (Strom, Strom, and Carbon) and the line blocking due to the violet system of cyanogen.

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BibTeX Citation

  author={Oinas, V.},
  title={Strong-line K stars. II. Chemical abundances},
  journal={Astrophys. J. Supp. Series},

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RIS Citation

ID  - oi05000f
AU  - Oinas, V.
PY  - 1974
TI  - Strong-line K stars. II. Chemical abundances
JA  - Astrophys. J. Supp. Series
VL  - 27
SP  - 405
EP  - 414
DO  - 10.1086/190303
ER  -

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