对银河系14颗s-过程超丰的post AGB星元素丰度分析

发布时间：2018-01-01 16:37

本文关键词：对银河系14颗s-过程超丰的post AGB星元素丰度分析　出处：《河北师范大学》2017年硕士论文　论文类型：学位论文

【摘要】：post AGB星已经完成了AGB星全部演化过程,它的元素丰度分布清晰的显示出AGB星最终的演化结果,分析它的元素丰度特征对于研究AGB星的形成及演化过程具有极其重要的地位。post AGB星元素丰度的研究重要的是在于对元素丰度结合观测数据和图像进行定量分析,其中元素包括α元素(O,Mg,Si,Ca,Ti),铁族元素(Sc,V,Cr,Fe,Co,Ni)和中子俘获元素(Y,Zr,Ba,La,Ce,Pr,Nd,Sm,Eu)。为了研究14颗银河系主要s-过程超丰的post AGB星的元素丰度异常的天体物理原因,我们采用五分量元素丰度模型计算拟合这些恒星元素丰度。结果表明,在[Fe/H]为-0.18到-0.91的范围内,14颗样本星主要s-过程分量系数Cs,m远高于太阳系的相应分量系数,弱r-过程分量系数Cr,w、弱s-过程分量系数Cs,w和Ia型超新星分量系数CI,a与太阳系的各分量系数很接近。比较特殊的是我们的样本星的主要r-过程分量系数Cr,m很大,这说明主要s-过程和主要r-过程对元素丰度的贡献都很重要。我们把14颗post AGB星与被引入的20颗已经确定主要r-过程和主要s-过程都超丰的恒星的元素丰度进行对比,发现它们元素丰度特征相似,这暗示样本星与20颗恒星有类似的天体物理起源。对于α元素,我们选取Mg元素、Si元素、Ga元素、Ti元素进行分析。它们的主要天体物理来源是大质量星的primary过程,但secondary分量贡献也很重要,而Ia超新星分量贡献可以忽略,它们的secondary分量贡献比例和Ia超新星分量贡献比例随[Fe/H]呈上升趋势,primary分量贡献比例随[Fe/H]呈下降趋势。对于铁族元素,选取Fe元素、Mn元素、Ni元素进行分析。Fe元素的primary分量贡献比例随[Fe/H]呈下降趋势,secondary分量贡献和Ia超新星贡献增大,尤其Ia超新星趋于主导贡献地位。Mn元素、Ni元素的secondary分量贡献稍高于primary分量和Ia超新星贡献,各分量贡献相对比较平稳。对于轻中子俘获元素,选取Y元素和Zr元素进行分析。它们的各分量贡献趋势比较平稳,其中主要s-过程贡献占主导地位,主要r-过程贡献也很大,而弱r-过程贡献趋势稍有下降,弱s-过程贡献可以忽略。对于重中子俘获元素,选取La元素、Nd元素、Sm元素、Eu元素和Gd元素进行分析。La元素、Nd元素、Sm元素的主要s-过程贡献占主导地位,但主要r-过程贡献也很大,而弱r-过程贡献可以忽略。Eu元素和Gd元素的主要r-过程分量贡献都占主导地位。主要s-过程分量对Eu元素的贡献不容忽视,甚至其对Gd元素的贡献与主要r-过程对Gd元素贡献基本持平。
[Abstract]:Post AGB star has completed the whole evolution process of AGB star, and its element abundance distribution clearly shows the final evolution result of AGB star. It is very important to study the formation and evolution of AGB star by analyzing its element abundance characteristics. The study of element abundance in AGB stars is very important for the quantitative analysis of element abundance in combination with observed data and images. The elements include the 伪 element, O, O, mg, Si, Ca, Ti, S, S, V, V, Cr, Fe, Co, Ni) and the neutron capture element, Y, Zr, Ba, Ba, La, ce. In order to study the astrophysical reasons for the anomalous elemental abundance of 14 major superabundant post AGB stars in the Milky way. We use the five-component element abundance model to calculate the fitting values of these stellar elements. The results show that. [In the range of -0.18 to -0.91, the main s- process component coefficients of 14 stars are far higher than those of the solar system, and the weak r-process component coefficients are much higher than those of the solar system. The weak S-process component coefficients CSW and Ia supernova component coefficients CIKA are very close to those of the solar system. What is more special is the main r-process component coefficient Cr of our sample stars. M is very large. This shows that both the main s- process and the main r- process contribute to the element abundance. We put 14 post. The AGB stars are compared with the element abundance of the 20 introduced stars that have identified both the major r-processes and the major S-processes. It is found that the characteristics of their element abundance are similar, which implies that the sample stars have a similar astrophysical origin with 20 stars. For the 伪 element, we select element mg and element Si, element Ga. The main astrophysical source of Ti element is the primary process of large mass star, but the contribution of secondary component is also very important, and the contribution of Ia supernova component can be neglected. Their secondary component contribution ratio and Ia supernova component contribution ratio are with each other. [The contribution ratio of primary component is increasing with Fe/H. [For iron group elements, the contribution ratio of primary component of Fe element, mn element and Ni element is determined with the increase of Fe element. [The secondary component contribution and the Ia supernova contribution of Fe/H are increasing, especially the dominant contribution of Ia supernova. The contribution of secondary component of Ni element is slightly higher than that of primary component and Ia supernova contribution, and the contribution of each component is relatively stable. Y element and Zr element are selected for analysis. The contribution trend of each component of these elements is relatively stable, in which the main sprocess contribution is dominant, and the main r-process contribution is also very large. However, the weak r-process contribution tends to decrease slightly, while the weak S-process contribution can be neglected. For heavy neutron capture elements, La element ND element Sm is selected. EU and Gd elements were analyzed. The main sprocess contribution of ND element Sm was dominant, but the main r-process contribution was also significant. But the weak r-process contribution can be neglected. Both the main r-process component contribution of Gd element and the main r-process component contribution to EU element can not be ignored. Even its contribution to Gd elements is basically the same as that of main r-processes.
【学位授予单位】：河北师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P156

【相似文献】