Statistical Properties of Barium Stars

Barium stars are G- and K-giant stars with atmospheric excesses of s-process elements, and a broadband spectral depression in the blue portion of the spectrum. The strength of the (lamda)4554 BaII line is used as a classification parameter known as the "barium Intensity". They have a mean absolute magnitude of <M> = 1.0 and a dispersion of (sigma) = 1.2 magnitudes (assuming a Gaussian distribution in absolute magnitude) as measured from secular and statistical parallaxes. These stars apparently belong to a young-disk population from analyses of both the solar reflex motion and their residual velocity distribution, which implies that they have an upper mass limit of around three solar masses. There is no apparent correlation of barium intensity with either luminosity or kinematic properties. The barium stars appear to be preferentially distributed in the direction of the local spiral arm, but show no preference to associate with or avoid the direction of the galactic center. They do not appear related to either the carbon or S-stars because of these tendencies and because of the stellar population to which each type of star belongs. The distribution in absolute magnitude combined with star-count analyses implies that these stars are slightly less numerous than previously believed. Barium stars show infrared excesses which correlate with their barium intensities. The reason for this is unknown, but could be related either to flux removed from the optical portion of the spectrum through line-blanketing or possibly to mass transfer in a binary system. Barium intensities can be identified from DDO photometric colors to approximately the same accuracy as obtained from the more tedious method of spectral analysis. This could prove to be a useful survey tool for the future identification of these stars.