r-过程核合成的场所和重元素丰度的离散

Sites for r-process Nucleosynthesis and Scatter of Abundance for Heavy Elements

首先考虑到随前身星质量增加Ⅱ型超新星爆发α元素的产量并不单调增加,从而导致Ⅱ型超新星所污染的星际气体的α元素丰度出现反转的因素,将贫金属星Ba的观测丰度分为2支,其中i支元素丰度产生于较低质量超新星,y支元素丰度产生于较高质量超新星,采用FM2004的Ⅱ型超新星爆发Mg元素的产量,利用Tsujimoto提出的方法,根据观测到的极贫金属星Ba和Mg丰度数值计算各种质量超新星r过程的产量,得出星系中r过程元素核合成的主要质量区间.然后,根据得到的不同质量Ⅱ型超新星r过程的产量关系,改进Fields等所提出的方法,解释观测到的贫金属星中子俘获元素的弥散性;另外,还根据3成份(晕、厚、薄盘)多相模型(气体、分子云、大小质量恒星以及剩余物质),利用所得到的产量计算了r过程元素的均匀化学演化.

The factor that the mass of ejected a-element does not always increase with the increasing of progenitor＇s mass,so α-element in the galactic interstellar medium （ISM） decrease at massive progenitor remnants is considered. The observed abundances of Ba are divided into two branches i and y. I-branch is the one produced in the minor type Ⅱ supernovae（SN Ⅱ ） and y-branch is the one produced in the massive SN Ⅱ . So Mg yields of FM2004 and the method of Tsujimoto are used, then main mass range of r-process are obtained. According to the obtained function of r-process yields and SN Ⅱ progenitor mass, the methods presented by fields are improved, scatter of n-capture elements in metal poor stars are explained. The model named three-zone multiphase model are used in order to study the chemical evolution of the Galaxy.