中小质量密近双星的演化及其初始-终止质量关系
文献类型：学位论文
| 作者 | 陈雪飞
|
| 学位类别 | 硕士 |
| 答辩日期 | 2002 |
| 授予单位 | 中国科学院研究生院（云南天文台） |
| 授予地点 | 北京 |
| 导师 | 韩占文 |
| 关键词 | 双星 密近-恒星 演化-白矮星 |
| 学位专业 | 天体物理 |
| 中文摘要 | 双星系统一直以来为人们所关注。对双星系统的研究解决了许多恒星物理上一直困绕我们的问题。近几年发展起来的大样本恒星演化需要单个双星系统或单星的性质作为物理输入，而以往单个双星系统的研究工作不能满足大样本恒星演化的需要。基于此，我们对中小质量密近双星的演化做了一个比较系统的研究。本文首先简单地回顾了双星演化的基本图象以及演化过程中出现的物理现象，然后比较详细地介绍了PPE恒星演化程序。最后，应用PPE程序，我们在一个较为密集的网格空间计算了150个星族I的密近双星模型。在计算中，假设洛希瓣物质交流（RLOF）不守恒-离开主星的物质有50％从系统丢失，丢失的物质单位质量带走的角动量与主星单位质量带有的角动量一致。混合长参量a取为2，对流超射通过参量δov（=0.12）加入。为了论文的完整和比较的方便，我们给出了守恒演化结果。我们在研究中发现，主星的终止质量（演化到白矮星之后的质量）对RLOF在赫氏空隙发生的起始点有较强的依赖性，并且这种依赖性会随质量增加而增加。但是，与RLOF过程质量与角动量守恒的结果相比，无论模型有没有加入对流超射，主星终止质量对双星系统初始质量比的依赖都不大。在qi=1.1时，我们拟合出了主星的终止质量Mlf与初始质量Mli和砒OF开始时主星半径R的关系，误差小于2.61％。此外，非守恒模型的RLOF过程似乎比守恒情形下更稳定。在我们的结果中，对初始质量比为4的模型，．只要主星初始质量不是特别小（≥2Me），RLOF过程总是动力学稳定的。而在守恒假设下，所有模型（qi＝4.0）的甩oF过程均为动力学非稳定。在讨论对流超射对模型的影响时我们注意到，由于对流超射的加入，恒星的He和C燃烧相对无超射模型有所提前，主星最终质量也有所增加（for111＞1．6五'）。但对于小质量双星，对流超射几乎没有什么影响。同时，我们还得到了一批低质量HeCO混合白矮星（-0.33M☉），Han在守恒的演化电也得到了同样的结果，表明低质量CO白矮星可以通过双星系统的CaseB演化形成，协阵由Marsh's小组观测得到的质量低于0.5M☉的白矮星（被认为是He白矮星）有一些可能是CO白矮星。 |
| 英文摘要 | Binary systems have been paid much attention for many years, and the study of them may account for many perplexing problems. Binary population synthesis (BPS), which has been developed in recent years, requires the properties of binary or single star as physical inputs. Previous studies are insufficient for the development of BPS, it is therefore necessary to make a systematic investigation on the evolution of low- and intermediate-mass close binary systems. In this thesis, I have reviewed the basic scenario of binary evolution firstly. And then, the computer code for stellar structure and evolution developed by Peter P. Eggleton is introduced in detail. I carry out 150 runs of non-conservative Population I binary evolution calculations. Convective overshooting is included via <5OV(=0.12) and I assume that 50 per cent of the mass lost from the primary during RLOF is lost from the system, carrying away the same specific angular momentum as the center of mass of the primary. For the integrity of the thesis and easy comparison, the results of the conservative evolution are also shown. I find that the remnant mass depends on when RLOF begins in the HG and the dependency increases with the primary mass. However, it does not depend much on the initial mass ratio, as compared to conservative cases. For qx =1.1,1 fit a formula for the remnant mass as a function of the initial mass Mif of the primary and the radius of the primary at the onset of RLOF with an error less than 2.61%. Furthermore, the non-conservative models seem more stable than conservative ones whether they include convective overshooting or not. In the result of our calculations, for the models of qi= 4, RLOF is always dynamical stable as long as the initial primary mass is not very small (≥2M⊙). However the RLOF of the conservative ones are all dynamical unstable in previous calculations. I have also discussed the influence of convective overshooting, which makes the final remnant masses larger (for Mli >1.6 M⊙) and also makes helium and carbon burning earlier. The convective overshooting has almost no effect on low-mass binaries, consistent with previous studies. During the study, I obtained many HeCO white dwarfs with low mass (-0.33 M⊙). Conservative calculations give similar result. These suggest that a low-mass CO white dwarf may be formed from stable RLOF in the HG, and therefore some of the presumed He white dwarfs observed may actually be CO white dwarfs. |
| 学科主题 | 天文学 |
| 语种 | 中文 |
| 公开日期 | 2016-05-03 |
| 页码 | 83 |
| 源URL | [http://ir.ynao.ac.cn/handle/114a53/4644]  |
| 专题 | 云南天文台_大样本恒星演化研究组 |
| 推荐引用方式 GB/T 7714 | 陈雪飞. 中小质量密近双星的演化及其初始-终止质量关系[D]. 北京. 中国科学院研究生院（云南天文台）. 2002. |
入库方式： OAI收割
来源：云南天文台
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