ABSOLUTE MAGNITUDES AND KINEMATICS OF BARIUM STARS

Theabsolutemagnitudeofbariumstarshasbeenob- tainedfromkinematicaldatausinganewalgorithmbasedonthe 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 (Mv = 1 m :5, M =0 m :5) seems to be an inhomogeneous group contain- ing barium binaries as well as AGB single stars. The most nu- merous group (about 150 stars) has a mean absolute magnitude corresponding to stars in the red giant branch (Mv =0 m :9, M =0 m :8). The third group contains barium dwarfs, the ob- tained mean absolute magnitude is characteristic of stars on the main sequence or on the subgiant branch (Mv =3 m :3, M =0 m :5). 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.