YNAO OpenIR  > 大样本恒星演化研究组
共生星的理论研究
Alternative TitleTheoretical Study of SymbioticStars
吕国梁
Subtype博士
Thesis Advisor韩占文
2006-06-23
Degree Grantor中国科学院研究生院(云南天文台)
Place of Conferral北京
Degree Discipline天体物理
Keyword双星 共生星-恒星 演化-吸积 吸积盘尘埃-新星
Abstract这是一篇关于共生星理论研究的博士论文。共生星因其壮观的光谱和光 变一直备受关注。共生星的光谱表明这类恒星系统是由一颗冷巨星、一颗热伴 星(可能是白矮星、中子星或者有吸积盘的主序星)和电离的星云组成。他们之 间复杂的相互作用为研究恒星演化理论和相互作用双星提供了激动人心的实验 室。本论文综述了共生星的观测特性和理论研究现状,并详细介绍了本人在攻 读博士学位期间在共生星理论研究领域的工作。 利用星族合成方法,我们分别对半相接共生星、分离共生星和D-型共生 星作了理论研究。利用主序星周围几何薄的吸积盘模型,我们模拟了半相 接共生星。此类共生星可能有两种不同物质转移方式:动力学非稳定的和 稳定的洛希瓣物质转移。这两种方式产生的半相接共生星的性质大不一样。 前者在银河系中的诞生率和数目分别是~0.056—0.045 yr-1和~5颗;后者的 分别是~0.002—0.005 yr-1和~60—280颗。通过和观测比较以及统计分析,共 生星AX Per 和CI Cyg (半相接共生星仅有的两个候选者)可能不是半相接 共生星。利用吸积白矮星表面热核爆发和星风吸积模型,我们建立了分离 共生星模型。研究结果表明,在银河系中,大约有1,200 — 15,000颗分离 共生星(在标准模型中,有4,300颗),每年大约有0.035—0.131颗分离共生星 诞生(在标准模型中,诞生率是0.076yr-1),平均每年发生1.3—13.5次共生星 新星爆发(在标准模型中,它的发生率是3.4yr-1),其中较弱的爆发每年发 生0.6—6.0次(在标准模型中,它的发生率是1.5yr-1),这依赖于模型的参数。 其中,最关键的两个物理参数是白矮星吸积星风物质的效率(它强烈地依赖 于共有包层的演化和星风速度)和白矮星表面吸积物质的临界点燃质量。在 研究中我们发现,共生星作为Ia-型超新星前身星,不是好的候选者。利用尘 埃模型,我们建立了D-型共生星模型。研究结果表明,在银河系中,D-型共 生星的诞生率范围从~0.001yr-1到~0.039yr-1(标准模型中为0.032yr-1),数目 从~250颗到~2,360颗(标准模型中为1,100颗)。D-型共生星占共生星总数的比例从2%到63%不等(标准模型中为26%),在大多数模型中,它大约是20%,这与观测符合。在D-型共生星模型中,最关键的物理参数星风速度。 通过对共生星的研究比较,我们发现分离共生星是共生星的主体。在共生星系统中,热伴星的平均质量大约是0.6M⊙, 冷伴星的平均质量大约 是 1.2M⊙,绝大多数轨道周期大于200天,这都与观测符合得很好。
Other AbstractThis paper is a theoretical doctorial thesis on the study of symbiotic stars. Their spectacular and photometric variability is a very important and attractive phenomenon. The spectra of symbiotic stars suggest that a three-component system consists of a binary with a hot component (white dwarf, neutron star or main-sequence star with an accretion disk ) and a cool component (red giant) and nebulae region. In this thesis, we summarize recent observational properties and theoretical study on symbiotic stars, and present the results of our studies on the field. By means of a population synthesis code, we have carried out a theoretical study of semi-detached symbiotic stars, detached symbiotic stars and D-symbiotic stars. In semi-detached symbiotic stars simulated by an accretion disks around main-sequence stars, there are two cases: dynamical unstable and stable Roche lobe overflow. To the first case, the birthrate of symbiotic stars is ~0.056 --- 0.045yr-1 and the number is ~5 in the Galaxy; to the stable Roche lobe overflow, the birthrate and the number are ~0.002 ---0.005yr-1 and ~60---280, respectively. By comparison with observations and statistic analysis, we consider that AX Per & CI Cyg (as the only candidates of semi-detached symbiotic stars ) may not be semi-detached symbiotic stars. For detached symbiotic stars simulated by thermonuclear runways on the surface of white dwarf accretor, we estimate the total number and the birthrate of detached symbiotic stars in the Galaxy as 1,200--- 15,000 (it is 4,300 in standard model) and ~0.035 ---0.131yr-2(it is 0.076yr-1 in standard model), respectively. The theoretical estimate of the Galactic occurrence rate of symbiotic novae is ~1.3 ---13.5yr-1(it is 3.4yr-1 in standard model), out of which weak symbiotic novae comprise from ~0.6 ---6.0yr-1(it is 1.5yr-1 in standard model). In all model assumptions, two crucial physical parameters for determination of the birthrate and number of detached symbiotic stars and novae are efficiency of accretion by white dwarfs (which greatly depends on the outcome of common envelope evolution and stellar wind velocity) and the mass of hydrogen layer which white dwarf can accumulate prior to hydrogen ignition. In our models, symbiotic stars are not likely progenitors of type Ia Supernovae. Using dust model, we construct theoretical model on D-symbiotic stars. We found that there are ~250---2,360 (it is 1,100 in standard model) D-symbiotic stars in the Galaxy. Their birthrate is between ~0.001---0.039yr-1(it is 0.032yr-1 in standard model) and the Galactic occurrence rate of D-symbiotic novae is ~0.8---5.4yr-1(it is 2.2yr-1 in standard model). The ratio of number of D-symbiotic stars to detached symbiotic stars is between 0.2% and 63%(it is 26% in standard model), and it is about 20% in most models, which is reasonable agreement with observations. In the model, the most crucial physical parameters is the stellar wind velocity of cool components. By comparison of two theoretical models, we find detached symbiotic stars are main population in symbiotic stars. In symbiotic stars, average masses of hot components and cool components are 0.6M⊙ and 1.2M⊙, respectively, and orbital periods are usually larger than 200 days, which agree with observations.
Subject Area天文学
Pages137
Language中文
Document Type学位论文
Identifierhttp://ir.ynao.ac.cn/handle/114a53/4650
Collection大样本恒星演化研究组
Recommended Citation
GB/T 7714
吕国梁. 共生星的理论研究[D]. 北京. 中国科学院研究生院(云南天文台),2006.
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