贫金属星r过程核合成相关问题的研究进展

快中子俘获过程(r过程)可以解释大约一半比铁重的稳定(和一些长寿命放射性的)富中子核素的产生,这已经被太阳系及各种金属丰度下恒星的观测结果所证实.为建立r过程模型,需要大量的核物理信息:涉及到β稳定谷与中子滴线之间的各种核素的稳定特性及β衰变分支等物理参数,实验和理论都面临巨大的挑战.综述了近年来贫金属星r过程核合成理...

Progress of the Study About R-process Nucleosynthesis in Metal-poor Stars

The rapid neutron-capture process(r-process) is traditionally believed to be responsible for the nucleosynthesis of approximately half of the heavy nuclei beyond the iron peak with long-decay half-lives in the solar material.In globular clusters and Galactic halo stars,the observed abundances show a nearly universal presence of r-process.With the rapid development of the abundance determinations,more elements(e.g.,Lu,Z = 71) are firstly detected in metal-poor r-process-enriched halo stars,which can be used as the r-process indicators for the early Galaxy.Moreover,these r-rich stars provide a strong constraint on the models of the r-process nucleosynthesis,especially the early galaxy chemical evolution of neutron-capture elements. Based on new atomic lab data,recent neutron-capture abundance comparisons between six r-rich Galactic halo stars and the Solar System r-only abundance distribution indicate that the heavier stable neutron-capture elements beyond Ba(Z>56) agree completely with a scaled solar system r-process abundance value.Nevertheless,the lighter neutron-capture elemental abundances in these stars are not in agreement with Solar-system r-only values. Although there is controversy over the origin of weak r-process,the neutron-capture elements are proposed to be formed possibly from multiple synthesis mechanisms,even if there exists little uncertainty.Whether the r-process at different astrophysical environments is diverse is also controversial. As needed for the r-process modelling,much effort has been put recently in the measurement of nuclear data of relevance to the r-process,including decay branch characteristics and nuclear stability properties of thousands of nuclides located between the valley of stability up to the neutron-drip line.The challenge is enormous in the theory and experiments of nucleosynthesis.In this paper,a review of r-process nucleosynthesis in metal-poor stars is presented outlining the development of theoretical models and their comparisons with observations.The distribution characteristics of abundance in main r-process and weak r-process stars,astrophysical r-process sites are also discussed separately together with the most recent observations. The outline of this paper is as follows.Firstly,this paper gives an overview of the significance on the r-process nucleosynthesis,including the present research conditions of this topic.Secondly,it summarizes the basic theory of r-process.And then we focus on the diversity of r-process nucleosynthesis:main r-process and weak r-process.Finally,as a comparison,we also review the study of r-process in the early Galaxy,especially the problems of CEMP stars,including both the observational and theoretical aspects.Although there is controversy over the nature of the weak r-process and CEMP-r/s stars,one thing is certain that these researches will be vital on constraining the models of r-process.