本文關(guān)鍵詞：對銀河系14顆s-過程超豐的post AGB星元素豐度分析　出處：《河北師范大學》2017年碩士論文　論文類型：學位論文

  更多相關(guān)文章： 恒星 post AGB 元素豐度

【摘要】：post AGB星已經(jīng)完成了AGB星全部演化過程,它的元素豐度分布清晰的顯示出AGB星最終的演化結(jié)果,分析它的元素豐度特征對于研究AGB星的形成及演化過程具有極其重要的地位。post AGB星元素豐度的研究重要的是在于對元素豐度結(jié)合觀測數(shù)據(jù)和圖像進行定量分析,其中元素包括α元素(O,Mg,Si,Ca,Ti),鐵族元素(Sc,V,Cr,Fe,Co,Ni)和中子俘獲元素(Y,Zr,Ba,La,Ce,Pr,Nd,Sm,Eu)。為了研究14顆銀河系主要s-過程超豐的post AGB星的元素豐度異常的天體物理原因,我們采用五分量元素豐度模型計算擬合這些恒星元素豐度。結(jié)果表明,在[Fe/H]為-0.18到-0.91的范圍內(nèi),14顆樣本星主要s-過程分量系數(shù)Cs,m遠高于太陽系的相應(yīng)分量系數(shù),弱r-過程分量系數(shù)Cr,w、弱s-過程分量系數(shù)Cs,w和Ia型超新星分量系數(shù)CI,a與太陽系的各分量系數(shù)很接近。比較特殊的是我們的樣本星的主要r-過程分量系數(shù)Cr,m很大,這說明主要s-過程和主要r-過程對元素豐度的貢獻都很重要。我們把14顆post AGB星與被引入的20顆已經(jīng)確定主要r-過程和主要s-過程都超豐的恒星的元素豐度進行對比,發(fā)現(xiàn)它們元素豐度特征相似,這暗示樣本星與20顆恒星有類似的天體物理起源。對于α元素,我們選取Mg元素、Si元素、Ga元素、Ti元素進行分析。它們的主要天體物理來源是大質(zhì)量星的primary過程,但secondary分量貢獻也很重要,而Ia超新星分量貢獻可以忽略,它們的secondary分量貢獻比例和Ia超新星分量貢獻比例隨[Fe/H]呈上升趨勢,primary分量貢獻比例隨[Fe/H]呈下降趨勢。對于鐵族元素,選取Fe元素、Mn元素、Ni元素進行分析。Fe元素的primary分量貢獻比例隨[Fe/H]呈下降趨勢,secondary分量貢獻和Ia超新星貢獻增大,尤其Ia超新星趨于主導貢獻地位。Mn元素、Ni元素的secondary分量貢獻稍高于primary分量和Ia超新星貢獻,各分量貢獻相對比較平穩(wěn)。對于輕中子俘獲元素,選取Y元素和Zr元素進行分析。它們的各分量貢獻趨勢比較平穩(wěn),其中主要s-過程貢獻占主導地位,主要r-過程貢獻也很大,而弱r-過程貢獻趨勢稍有下降,弱s-過程貢獻可以忽略。對于重中子俘獲元素,選取La元素、Nd元素、Sm元素、Eu元素和Gd元素進行分析。La元素、Nd元素、Sm元素的主要s-過程貢獻占主導地位,但主要r-過程貢獻也很大,而弱r-過程貢獻可以忽略。Eu元素和Gd元素的主要r-過程分量貢獻都占主導地位。主要s-過程分量對Eu元素的貢獻不容忽視,甚至其對Gd元素的貢獻與主要r-過程對Gd元素貢獻基本持平。
[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 偽 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 偽 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.
【學位授予單位】：河北師范大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：P156

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