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Taking account of the metallicity dependence of the s-process nucleosynthesis in the AGB stars, we adopted the wind accretion model with the condition of total angular momentum conservation and used the Monte-Carlo method to study the variations and the distributions of the orbital elements of the mild and strong Ba stars. The calculated results show that the level of heavy-element overabundance in a Ba star depends on the orbital period. Since there is a strong dependence of s-process yields on the initial stellar metallicity of the AGB star and a strong increase of the s-process yields in AGB stars with decreasing metallicity, the calculated results strongly suggest that the initial metallicity of the Ba star systems is another important parameter for the level of heavy-element overabundance in a Ba star. The strong Ba stars generally have lower metallicities than mild Ba stars. The masses of AGB progenitor and Ba star are other two parameters which also have some impact on the heavy-element overabundance in the Ba star. [ABSTRACT FROM AUTHOR]

The supernova yields of r-process elements are obtained as a function of the mass of their progenitor stars from the abundance patterns of extremely metal-poor stars on the left-side [{Ba/Mg}]--[{Mg/H}] boundary with a procedure proposed by Tsujimoto and Shigeyama. The ejected masses of r-process elements associated with stars of progenitor mass M ms ≤ 18 M ⊙ are infertile sources and the SNe II with 20 M ⊙ ≤ M ms ≤ 40 M ⊙ are the dominant source of r-process nucleosynthesis in the Galaxy. The ratio of these stars 20 M ⊙ ≤ M ms ≤ 40 M ⊙ with compared to the all massive stars is about∼ 18%. In this paper, we present a simple model that describes a star's [ r/Fe] in terms of the nucleosynthesis yields of r-process elements and the number of SN II explosions. Combined the r-process yields obtained by our procedure with the scatter model of the Galactic halo, the observed abundance patterns of the metal-poor stars can be well reproduced. [ABSTRACT FROM AUTHOR]