Astron. Astrophys. 363, 692-704 (2000)

Chemical abundances in cool metal rich disk dwarf stars ^*

P. Thorén ¹ and S. Feltzing <sup>2

1</sup> Uppsala Astronomical Observatory, Box 515, 751 20 Uppsala, Sweden
² Lund Observatory, Box 43, 221 00 Lund, Sweden

Received 5 June 2000 / Accepted 17 September 2000

Abstract

The present study of spectra of twelve metal-rich cool dwarf stars, carefully selected in order to cover a range of temperatures ( K), is a follow up on Feltzing & Gustafsson (1998) with the aim to understand the apparent over-ionization and anomalous elemental abundances found by them for the K dwarf stars in their sample.

Our method of analysis employs synthetic spectra of the full spectrum both to constrain the continuum level and to derive abundances. It is shown that by using this method and imposing a strict excitation equilibrium (possible to do because of the care in selection of observed Fe I lines) we are able to show that metal-rich K dwarf stars do not show anomalous stellar abundances, as indicated in Feltzing & Gustafsson (1998), and can, with reasonable efforts, be analyzed in order to increase the number of metal-rich stars with useful chemical abundances.

With abundance analysis by means of spectrum synthesis and assuming Local Thermodynamic Equilibrium (LTE) the abundances of Na, Si, Ca, Sc, Ti, V, Cr, Fe, Co, Ni, and Nd have been derived. Also ionization balance is satisfied for Fe and Cr after correcting the stellar effective temperatures such that both ionization and excitation equilibrium were satisfied.

In addition, spectra from five cool dwarf stars of the Feltzing & Gustafsson (1998) sample have been analyzed with the methods used in this work. They show essentially the same abundance patterns as the new stars in this sample.

Key words: stars: late-type stars: abundances

* Based on observations made at ESO, La Silla

Send offprint requests to: Patrik Thorén

SIMBAD Objects

Contents

• 1. Introduction
• 2. Observations
  • 2.1. Selection of objects
  • 2.2. Selection of wavelength regions
  • 2.3. Instrumental setup and observations
• 3. Reductions and abundance analysis
  • 3.1. Basic reduction steps
  • 3.2. Scattered light
  • 3.3. Stellar parameters
  • 3.4. Model atmospheres
  • 3.5. Atomic line data
  • 3.6. Abundance determinations
  • 3.7. Error budget from the analysis
    • 3.7.1. NLTE effects in Fe I and Ca I
    • 3.7.2. Line data
    • 3.7.3. Continuum fitting
    • 3.7.4. Background subtraction
    • 3.7.5. Instrumental profile and macroscopic stellar broadening
    • 3.7.6. Synthetic line profile fitting
    • 3.7.7. Errors in derived abundances due to errors
      in stellar parameters
    • 3.7.8. Summary of the error analysis
  • 3.8. Comparison with other works
• 4. Stellar abundances
  • 4.1. Summary and speculations
• 5. Discussion
• 6. Conclusions
• Acknowledgements
• Appendix: atomic line data for the LTE analysis
• References

© European Southern Observatory (ESO) 2000

Online publication: December 11, 2000
helpdesk.link@springer.de