The Abundance Proportion Study Of Main R-process And Weak R-process In Metal-poor Stars

The metal-poor stars are known as the stellar evolution history of the "fossil." In order to test nucleosynthesis theories and exploration of star formation, it is important to study the nucleosynthesis element abundance. In contrast to the great prograss in the study of the s-process element formation occurring in low- and intermediate-mass AGB stars, it is still unclear on the nature of r-process in the high neutron density, which is believed to take place in the explosive stage of stellar evolution. It is still not well-determined for the contribution rate of nucleosynthesis process to the neutron capture element.Using the parametrical method in this paper, we study the proportion coefficients of the main r-process and weak r-process in metal-poor stars based on the elemental nuclei synthesis theory. We obtain the correlation between the [Eu/Fe] and the main r-process ratio coefficient (Km) of light and neutron-capture elements. By comparing the predicts and observations from these relations, we find that the neutron-capture elements are produced via at least two individual nucleosynthesis process: the main r-process and the weak r-process. Heavy Neutron Capture Elements are mainly produced from the main r-process, while light Neutron Capture Elements are mainly formed from the weak r-process. Furthermore, we also find that the coefficient of each element is obviously different in metal-poor sample stars, which means that these nucleosynthesis process may be produced from several different sites.From the studies on the chemical evolution in early galaxy and the parametrical model of light elements and heavy neutron-capture elements, it can be seen that s- and r-process can be divided into two components or two individual nucleosynthesis process to calculate the contributory percentage of element abundances. Thus, this would be able to quantify the nucleosynthesis process to component coefficients, which can evaluate key nucleosynthesis component and know the physical environment and site of star formation. Although there are shortcomings in the model, to be sure, for the r-rich-process stars with a lot of the observed elemental abundances, this method may well be an effective appoach.