Strong Barium Stars With Weak Barium Star Monte-carlo Simulation

It is very significant to Ba stars for heavy-element nucleosynthesis and Galactic chemical evolution. The obvious overabundance of heavy-element are observed in Ba stars, however, owing to the luminosity of Ba stars is too faint, so we contemplate it has not evolved into the stage of AGB, and the nuclear ⁹⁹Tc have not observed in Ba stars. In general, Ba stars belong to binary system, and their heavy-element overabundance are due to the accreting material from the companions (the former TP-AGB stars and the present white dwarfs).Carrying out a series of Monte-Carlo simulations, the works of orbital elements of binaries are recalculated considering the influence of initial metallicity on S-process nucleosynthesis of intrinsic AGB stars,and here we adopt wind accretion scenario with the total angular momentum conservation. The calculation demonstrate that in the course of wind accretion, in the mass-losing stage of the wind the orbital semi-major axis increases,and result in the orbital period increases, but the eccentricity dose not vary significantly. This can simulate and interpret the observational facts that are as to the orbital elements and abundance distribution . On the basis of the calculation and discuss with respect to the orbit elements and heavy—element abundance, our results show the following conclusions:(a)the period of logarithm distribution of G-K red giant binaries that evolved into mild barium stars is even. The are still orbital distribution for periods longer than 10000 days and the G-K red giant binaries that evolved into strong barium stars are dense in the region of short periods. The reason lie in that, the shorter the orbital period of the binary system ,the larger the mass accretion, and the higher the heave-element abundance. So it is easier for red giant binaries evolve into strong barium stars with shorter orbital period.(b)for lower-mass AGB stars, due to a smaller metallicity in the He stratum probably result in larger heavy-element overabundances , therefore the barium abundance of binary system increase with the decline of initial metallicity on condition that other factors are equal.(c)there is little relationship between the variation of the first star initial mass and the distribution of Ba—stars abundance, but the distribution of its number decline with increasing initial mass of first stars .the distribution of Ba—abundance in strong barium stars...