Exploring the nucleosynthesis region of metal-poor Stars
The chemical abundances of the very metal poor double-enhanced stars are excellent information to set new constraints on models of neutron-capture processes at low metallicity. There have been many theoretical studies of s-process nucleosynthesis in low-mass AGB stars. Using the parametric approach based on the radiative s-process nucleosynthesis model,we cal culate the following five parameters for a series of metal-poor stars. They are: the mass fraction of 13C pocket q,the overlap factor r,the neutron exposure per interpulse △T,and the component coefficients that correspond to relative contribution from the s-process and the r-process. We find that the mass fraction of 13C pocket q deduced for the Pb stars is comparable to the overlap factor r,which is about 10 times larger than normal AGB model; q～0.05; and the neutron exposure per interpulse △T for all Pb stars are about 10 times smaller than the ST case (△Ｔ～7.0mb-1). Although the two fundamental parameters △T and q obtained for the Pb stars are very different from the AGB stellar model,the results of the larger value of q and the smaller value of △T can also explain the abundance distribution of the Pb stars. This suggest that the q change to larger than that of normal AGB model. Then,this factor will result in the descent of the density of 13C in the nuclear synthesis region directly. So,the neutron exposure △T will also decrease to the same extent. Although the neutron number density in the larger initial mass AGB stars (m> 3M☉) is high,the neutron irradiation time is shorter,obviously the neutron exposure per interpulse in the AGB stars should be smaller. It is noteworthy that the total amount of 13C in metal poor condition is close to the ST case,which is consistent with the primary nature of the neutron source.
Nucleosynthesis metal-poor Stars
Yuan-Yuan Geng Dong-Nuan Cui Jiang Zhang Bo Zhang
Department of Physics,Hebei Normal University,113 Yuhua Dong Road,Shijiazhuang 050016,P.R.China
国际会议
The 252th Symposium of the International Astronomical Union(国际天文学联合会第252届研讨会)
海南三亚
英文
339-340
2008-04-06（万方平台首次上网日期，不代表论文的发表时间）