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Astron. Astrophys. 319, 881-885 (1997)

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Absolute magnitudes and kinematics of barium stars *

A.E. Gómez 1, X. Luri 2, S. Grenier 1, L. Prévot 3, M.O. Mennessier 4, F. Figueras 2 and J. Torra 2

1 Observatoire de Paris-Meudon, D.A.S.G.A.L., F-92195 Meudon Cedex, France
2 Departament d'Astronomia i Meteorologia, Universitat de Barcelona, Avda. Diagonal 647, E-08028, Barcelona, Spain
3 Observatoire de Marseille, 2, Place Le Verrier, F-13248 Marseille Cedex 4, France
4 Universite de Montpellier II, G.R.A.A.L., F-34095 Montpellier Cedex 5, France

Received 15 May 1996 / Accepted 29 July 1996

Abstract

The absolute magnitude of barium stars has been obtained from kinematical data using a new algorithm based on the maximum-likelihood principle. The method allows to separate a sample into groups characterized by different mean absolute magnitudes, kinematics and z-scale heights. It also takes into account, simultaneously, the censorship in the sample and the errors on the observables. The method has been applied to a sample of 318 barium stars. Four groups have been detected. Three of them show a kinematical behaviour corresponding to disk population stars. The fourth group contains stars with halo kinematics.

The luminosities of the disk population groups spread a large range. The intrinsically brightest one ([FORMULA], [FORMULA]) seems to be an inhomogeneous group containing barium binaries as well as AGB single stars. The most numerous group (about 150 stars) has a mean absolute magnitude corresponding to stars in the red giant branch ([FORMULA], [FORMULA]). The third group contains barium dwarfs, the obtained mean absolute magnitude is characteristic of stars on the main sequence or on the subgiant branch ([FORMULA], [FORMULA]). The obtained mean luminosities as well as the kinematical results are compatible with an evolutionary link between barium dwarfs and classical barium giants. The highly luminous group is not linked with these last two groups. More high-resolution spectroscopic data will be necessary in order to better discriminate between barium and non-barium stars.

Key words: stars: absolute magnitude – barium stars – kinematics

* Table 2 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: A.E. Gómez

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© European Southern Observatory (ESO) 1997

Online publication: July 3, 1998
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