Impact Of Metal Abundances On S-process Nucleosynthesis Parameters In AGB Stars

In this aer,we use the convection model and the single neutron exosures model,to calculate 26 barium stars and 29 very metal-oor stars.1.The convection model:the calculation results show that the overla factor r of most metal-poor stars is high,the overla factor r of of Ba stars is low.It results the metal-poor stars arc more easily roduced the heavy element abundances than Ba stars while neutron exposures of most metal-poor stars is greater than that of Ba stars.Since the reasons ¹³C neutron source is primary neutron,the typical neutron density in the nucleosynthesis zone scales roughly as 1/Z^0.6.Because the neutron exosure of the metal-poor stars is high, neutron exosure of Ba stars is lower,it results in the metal-poor stars abundance ratio of [Pb/hs]is higher than in Ba stars.The r-process-component coefficient of metal-poor stars stars is high,while the Ba stars is low.The s-process component coefficient C_s of most metal-poor stars is greater,but the Ba stars is lower,and the mass of Ba stars is probably greater than metal-poor stars.2.The single neutron exposures model:the neutron exposures of most metal-poor stars is high,but the Ba stars is low,so the ¹³C neutron source is primary neutron.The r-process-component coefficient of metal-poor stars is 0 to 90,while the Ba stars is between 1 and 5.Ba stars of the high metal abundance and low neutron exposure,single neutron exposures can not produce the sufficient lead.This implies single neutron exposures model is not fit for most Ba stars.3 Comparison of two models:for Ba stars,there is strong correlation between their△τandÏ„₀.The two model calculations of s-process are nearly equal on the condition of C_s＜0.001.Granting that C_s is less than 0.001,the convection model calculation of C_s is higher than that of the single neutron exposures model.For barium stars,the convection model is fit with x²ï¼œ4 while the two models is nearly similar with x²ï¼ž4.In addition to individual cases(r＜0.1),the convection model is better than single neutron exposures model. For metal-poor stars,when the neutron exposure is 0.5 to 1mbarn^-1,it is have not storng corrrelation.On the other hand,there is storng corrrelation when neutron exposure is between 3 and 5mbarn^-1.For as much as s-process component coefficient C_s is similar in two models, the value that the two models gives the similar dilution.The convection model results is rather than a single neutron exposures model in addition to r＜0.1 and r＞0.9.Simultaneously r-process component coefficient C_r is also similar in two models,the value presents that C_r has nothing to do with nucleosynthesis model AGB-stars.