【摘要】 最近的研究结果表明,目前流行的¹³C壳层(¹³C pocket)在热脉冲间隔期间辐射燃烧的低质量AGB（Asymptotic Giant Branch）星s-过程核合成模型,其核合成区域的中子辐照量分布可视为指数形式,平均中子辐照量τ0和模型参量之间的关系为τ0=-?τ/ln[q/（1-r+q）],式中?τ为每次照射的中子辐照量,r为重叠因子,q为¹³C壳层占氦中间壳层的质量比例.利用文献中参数化AGB星s-过程核合成模型对20颗CEMP（Carbon-Enhanced Metal-Poor）-s和CEMP-s/r星观测丰度的拟合结果,对该平均中子辐照量计算公式的可靠性进行了检验,并初步探讨其在重元素s-过程核合成理论研究中的作用.研究结果表明:在辐射s-过程核合成机制下,对于经历连续多次中子照射的CEMP星,公式是适用的;和参数化AGB星s-过程核合成模型结合,公式可以作为单辐照或特殊CEMP星的一个有效筛选工具.考虑到¹³C壳层的不确定性,公式在理解CEMP星中子俘获元素观测丰度产生的物理条件方面的作用值得做进一步的探讨.更多还原

【Abstract】 Recent studies have shown that, for the current s-process nucleosynthesis model for the low-mass asymptotic giant branch（AGB） stars with¹³C pocket radiative burning during the interpulse period, the neutron exposure distribution in the nucleosynthesis region can be regarded as an exponential function, and the relation between the mean neutron exposure τ0and the model parameters is τ0=-?τ/ln[q/（1-r + q）],in which ?τ is the exposure value of each neutron irradiation, r is the overlap factor,and q is the mass ratio of the¹³C shell to the He intershell. Using the published data resulted from fitting the observed abundances of neutron-capture elements in 20 CEMP（Carbon-Enhanced Metal-Poor）-s and CEMP-s/r stars with the parametric AGB stellar s-process model, the reliability of the derived formula is tested, and further more the application of the formula in the s-process nucleosynthesis study is explored preliminarily. Our results show that, under the radiative s-process nucleosynthesis mechanism,the formula is suitable for CEMP stars experiencing recurrent neutron exposures. Combined with the parametric AGB nucleosynthesis model, the formula could be regarded as an effective tool to screen the CEMP stars with a single neutron exposure or a special type. Considering the uncertainty of the ¹³C pocket, the role of this formula in understanding the physical conditions necessary to reproduce the observed s-process abundances in CEMP stars needs further study.更多还原