本文選題：恒星演化 + 熱脈沖AGB星��； 參考：《浙江師范大學(xué)》2011年碩士論文

【摘要】：在恒星演化過程中湍流壓常被忽略,但其對(duì)流區(qū)固有的大尺度湍流使得湍流壓必然存在。本文通過對(duì)3～10M⊙恒星在赫羅圖上演化軌跡的研究,并分析恒星內(nèi)部氦殼層燃燒峰值處能量、密度、溫度、氦殼層表面光度與恒星表面光度比及恒星半徑的變化,給出了中等質(zhì)量恒星由早期AGB星演化至熱脈沖AGB星階段在赫羅圖上的分界點(diǎn),與119顆碳星的觀測(cè)結(jié)果吻合得相當(dāng)好。同時(shí)提出：在恒星演化至該分界點(diǎn)之后,其星風(fēng)物質(zhì)損失公式可能需要引入一個(gè)與表面光度無關(guān)的量以主導(dǎo)超星風(fēng)的形成。在此基礎(chǔ)上,通過對(duì)考慮湍流壓效應(yīng)下5Mo恒星的結(jié)構(gòu)和演化及星風(fēng)物質(zhì)損失率的分析,發(fā)現(xiàn)湍流壓在熱脈沖AGB星階段對(duì)星風(fēng)物質(zhì)損失影響較大,從而使得熱脈沖AGB星的湍流壓不可忽略。 在慮及湍流壓對(duì)星風(fēng)物質(zhì)損失的可能影響之后,我們對(duì)恒星的外殼進(jìn)行了詳細(xì)的分析,以期了解湍流在超星風(fēng)形成機(jī)制中所扮演的可能角色。通過對(duì)恒星演化過程中恒星外殼對(duì)流區(qū)馬赫數(shù)極大值處各種壓強(qiáng)、對(duì)流元馬赫數(shù)、引力加速度、及該處以外質(zhì)量大小的分析,發(fā)現(xiàn)恒星外殼對(duì)流區(qū)出現(xiàn)的可壓縮流體對(duì)恒星質(zhì)量損失存在一定的影響,從而嘗試在考慮星風(fēng)物質(zhì)損失機(jī)制時(shí)引入可壓縮流體機(jī)制,提出新的星風(fēng)物質(zhì)損失公式。 應(yīng)用新的星風(fēng)物質(zhì)損失公式對(duì)3～5M⊙恒星質(zhì)量損失率進(jìn)行計(jì)算,并將其與經(jīng)典星風(fēng)物質(zhì)損失公式的計(jì)算結(jié)果對(duì)比。發(fā)現(xiàn)從主序直至中心氦核燃燒結(jié)束階段,新的星風(fēng)物質(zhì)損失公式計(jì)算所得星風(fēng)物質(zhì)損失率與經(jīng)典星風(fēng)物質(zhì)損失公式計(jì)算結(jié)果幾近一致,在后期則不受光度影響產(chǎn)生了持續(xù)的較大的星風(fēng)物質(zhì)損失率,比較符合實(shí)際觀測(cè)結(jié)果。
[Abstract]:In the process of star evolution, turbulence pressure is often ignored, but the large scale turbulence inherent in the convection region makes the turbulence pressure inevitable. In this paper, we study the evolution track of 310M ~ (-) star on Hero diagram, and analyze the changes of energy, density, temperature, surface luminosity of helium shell and star radius at the peak value of helium shell burning in the interior of the star, and the relation between the surface luminosity of the helium shell and the surface luminosity of the star. The boundary points of the medium mass stars from the early AGB stars to the thermal pulse AGB stars on the Hero diagram are given, which are in good agreement with the observations of 119 carbon stars. At the same time, it is suggested that after the star evolves to the boundary point, it may be necessary to introduce a quantity independent of surface luminosity to dominate the formation of superstar wind. On the basis of the analysis of the structure and evolution of 5Mo stars and the loss rate of stellar wind matter considering the turbulent pressure effect, it is found that the turbulent pressure has a great influence on the loss of stellar wind matter in the thermal pulse AGB star stage. Thus the turbulent pressure of the thermal pulse AGB star can not be ignored. After taking into account the possible influence of turbulence pressure on the loss of stellar wind material, we have made a detailed analysis of the shell of a star in order to understand the possible role of turbulence in the formation mechanism of superstar wind. Based on the analysis of various pressures, Mach numbers of convection elements, gravitational acceleration, and mass outside the convective region of a star during the evolution of a star, the maximum value of Mach number in the convection region of a star is analyzed. It is found that the compressible fluid in the convective region of the stellar shell has a certain influence on the mass loss of the star. Therefore, the compressible fluid mechanism is introduced into account of the mechanism of the stellar wind mass loss, and a new formula for the loss of the stellar wind mass is proposed. The mass loss rate of the star is calculated by using the new formula of stellar wind mass loss, and the results are compared with those of the classical formula of stellar wind mass loss. It is found that from the main sequence to the end of the central helium core combustion, the calculated results of the new formula for calculating the loss rate of the star wind matter are almost consistent with the results of the classical formula for the star wind mass loss. In the later stage, the star wind material loss rate is large and consistent with the observed results.
【學(xué)位授予單位】：浙江師范大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2011
【分類號(hào)】：P144

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本文編號(hào)：1932372