银盘恒星元素丰度的研究

发布时间：2018-06-09 00:53

本文选题：银盘 + 恒星　；参考：《河北师范大学》2015年硕士论文

【摘要】：观测表明,银盘不同的中子俘获元素丰度随金属丰度变化有不同的趋势。研究银河系恒星的形成机制、演化过程对我们来说非常重要,它是我们理解其他星系恒星形成及演化过程的一个重要参考样本。并且已经有很多关于银河系恒星形成及演化过程的研究成果,但仍有些问题是没有被理解的。元素的天体物理来源是多样的,其涉及的物理过程也极其复杂。在这种情况下,观测的恒星元素丰度不能用单一的核合成过程来解释。为了揭示银河系恒星复杂的形成历史和演化过程,本文采用五分量元素丰度模型对样本星进行拟合。我们在计算时选择的元素范围包括了α元素、铁族元素和中子俘获元素,通过对计算结果分析我们得到了银盘恒星中各元素来源情况。本文主要包括以下两部分:第一部分首先给出本文所采用的五分量元素丰度模型及计算方法,其次对233颗银盘恒星元素丰度进行计算拟合,并给出最佳拟合结果。通过对整体拟合效果的分析,得知我们的计算方法是有效的。最后对计算结果进行分析和讨论。第二部分给出本文结论。随着恒星金属丰度的增加,主要r-过程和弱r-过程对元素丰度的贡献不断减少,而主要s-过程、弱s-过程和Ia型超新星对元素丰度的贡献相对增多。此外,我们还得到了每个元素(O、Mg、Si、Ca、Y、Zr、Ba、La、Ce、Nd、Sm、Eu)的[X/O]随[Fe/H]增加的变化趋势及天体物理原因。对于α元素,大质量星primary分量的贡献处于主导地位,所以[α/Fe]随[Fe/H]增加都有下降趋势。但是由于secondary分量的贡献随[Fe/H]增加而增加,一旦secondary分量贡献比例逐渐接近primary分量贡献比例,则[α/Fe]随[Fe/H]增加而下降的趋势相对较平缓。对于铁元素,[Fe/Fe]=0的天体物理原因应该解释为Ia型超新星的贡献。而对于元素Ni,在富金属丰度部分,[Ni/Fe]随[Fe/H]呈现上扬趋势的原因是secondary分量和Ia型超新星的贡献。对于中子俘获元素,[X/Fe]随[Fe/H]的增加有不同变化趋势的天体物理原因应该由不断增加的主要s-过程分量的贡献来解释。而对于元素Sm、元素Eu,主要r-过程分量的贡献一直处于主导地位。
[Abstract]:The results show that the neutron capture element abundance of silver disk varies with the metal abundance. It is very important for us to study the formation mechanism of stars in the Milky way. It is an important reference sample for us to understand the formation and evolution of stars in other galaxies. And there have been a lot of research on the formation and evolution of stars in the Milky way, but there are still some problems that have not been understood. Astrophysical sources of elements are diverse and the physical processes involved are extremely complex. In this case, the observed stellar element abundance cannot be explained by a single nuclear synthesis process. In order to reveal the complex formation history and evolution process of stars in the Milky way, a five-component element abundance model is used to fit the sample stars. The range of elements we select in the calculation includes alpha element, iron group element and neutron capture element. Through the analysis of the calculated results, we obtain the source of each element in the silver disk star. This paper mainly consists of the following two parts: in the first part, the five-component element abundance model and its calculation method are given. Secondly, the element abundance of 233 silver disk stars is calculated and fitted, and the best fitting results are given. Through the analysis of the whole fitting effect, we know that our calculation method is effective. Finally, the calculation results are analyzed and discussed. The second part gives the conclusion of this paper. With the increase of star metal abundance, the contribution of main r-process and weak r-process to elemental abundance decreases, while that of main sprocess, weak-s-process and Ia-type supernova increases relatively. In addition, the variation trend of [X / O] with [Fe / H] increase and the cause of astrophysics for each element O _ (O) MgO _ (Si-Si) Ca ~ (2 +) YC ~ (2 +) Zr ~ (2 +) ~ (2) ~ (2 +) ~ (1) with increasing of [Fe / H] are also obtained. For the 伪 element, the contribution of the primary component of the mass star is dominant, so [伪 / Fe] decreases with the increase of [Fe / H]. However, as the contribution of secondary component increases with the increase of [Fe / H], once the contribution ratio of secondary component is closer to that of primary component, the trend of [伪 / Fe] decrease with [Fe / H] increase is relatively gentle. For the iron element, the astrophysical cause of [Fe / Fe] 0 should be explained as the contribution of type Ia supernova. For the element Ni, in the rich metal abundance part, [Ni / Fe] shows an upward trend with [Fe / H] because of the contribution of secondary component and Ia type supernova. For neutron capture elements, the astrophysical reasons that [X / Fe] have different trends with increasing [Fe / H] should be explained by the contribution of increasing major s- process components. The contribution of the main r-process component to the element Sm, Eu-is always dominant.
【学位授予单位】：河北师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P148

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