Neutron Capture Elements In Super-abundance Metal-poor Stars The Abundance Of Simulation And Analysis

The large modern surveys for metal-poor stars have unveiled the existence of stars in which the abundances of neutron-capture elements are greatly enhanced. These stars exhibit great enhancement of s-process elements or r-process elements or both, we shall denote these stars neutron-enhanced metal-poor (NEMP) stars. According to the recent observation we propose [C/Fe] to be the arbitrary location of the class boundaries and investigate the relations between s+r stars; s- stars and r- stars, in which models of early Galactic chemical evolution and extrinsic AGB stars were taken into account in our calculation.We suggest that the s+r stars may originate from a former 4-5M_⊙companion in a wide binary system, which may undergo s-processing during an AGB phase, followed by r-process during its subsequent supernova explosion. The material of s-process and r-process the secondary received may be less with the distance between the binary became wider. s-stars and s+r stars may belong to the same category. The s-stars may originate from binaries with wider orbital separation or binaries with lower primary core mass, which cannot satisfy the physical conditions to produce r-element type 1.5 supernovae (SNe 1.5) required. Since the formation of SN 1.5 is more difficult for a binary system with high metallicity, (Zijlstra 2004) the upper limit of metallicity (Fe/H < -2.0) for the observed double enhanced stars could be explained.We find the simulation for binary systems with a star of 5-8 M_⊙is in good agreement with the observed data. This may give a probable candidate site for nucleosynthesis of the r-process elements and provide reasonable explanation for the different distribution between the large scatter of r-process elements and small for alpha elements.