Astron. Astrophys. 326, 722-730 (1997)

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Barium stars, galactic populations and evolution ^{* **}

M.O. Mennessier ¹, X. Luri ², F. Figueras ², A.E. Gómez ³, S. Grenier ³, J. Torra ² and P. North <sup>4

1</sup> Université de Montpellier II and CNRS, G.R.A.A.L., F-34095 Montpellier Cedex 5, France
² Departament d'Astronomia i Meteorologia, Universitat de Barcelona, Avda. Diagonal 647, E-08028, Barcelona, Spain
³ Observatoire de Paris-Meudon, D.A.S.G.A.L., F-92195 Meudon Cedex, France
⁴ Institut d'Astronomie de l'Université de Lausanne CH-1290 Chavannes des Bois, Switzerland

Received 2 April 1997 / Accepted 30 April 1997

Abstract

In this paper HIPPARCOS astrometric and kinematical data together with radial velocities from other sources are used to calibrate both luminosity and kinematics parameters of Ba stars and to classify them. We confirm the results of our previous paper (where we used data from the HIPPARCOS Input Catalogue), and show that Ba stars are an inhomogeneous group. Five distinct classes have been found i.e. some halo stars and four groups belonging to disk population: roughly super-giants, two groups of giants (one on the giant branch, the other at the clump location) and dwarfs, with a few subgiants mixed with them. The confirmed or suspected duplicity, the variability and the range of known orbital periods found in each group give coherent results supporting the scenario for Ba stars that are not too highly massive binary stars in any evolutionary stages but that all were previously enriched with Ba from a more evolved companion. The presence in the sample of a certain number of "false" Ba stars is confirmed. The estimates of age and mass are compatible with models for stars with a strong Ba anomaly. The mild Ba stars with an estimated mass higher than 3 may be either stars Ba enriched by themselves or "true" Ba stars, which imposes new constraints on models.

Key words: stars: abundances; distances; kinematics; evolutiongalaxy: stellar content

* Based on data from the ESA HIPPARCOS astrometry satellite
** Table 4 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html

Send offprint requests to: M.O. Mennessier

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Contents

• 1. Introduction
• 2. Classification from HIPPARCOS data
  • 2.1. Sample and data
  • 2.2. The LM method
  • 2.3. Number of groups and mean parameters
  • 2.4. Classification of stars and individual luminosities
• 3. Discussion
  • 3.1. Ages and masses
  • 3.2. Duplicity
  • 3.3. Variability
  • 3.4. Ba intensities
• 4. Conclusion
• Acknowledgements
• References

© European Southern Observatory (ESO) 1997

Online publication: October 15, 1997
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