| 相接双星的物理过程研究 |
| 其他题名 | A study of physical processes in the contact binary
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| 宋汉峰
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| 学位类型 | 博士
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| 导师 | 黄润乾
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| 2006-07-21
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| 学位授予单位 | 中国科学院研究生院（云南天文台）
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| 学位授予地点 | 北京
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| 学位专业 | 天体物理
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| 关键词 | 相接双星
物质交换和平衡条件
质量与能量交换过程
通过外拉格朗日点的物质和角动量损失
转动与潮汐效应
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| 摘要 | 在众多的恒星中，双星占据一半以上。在双星中有一类特殊的双星称为相接双星，他们的特点是两颗子星都充满洛希瓣，双星间可以发生双向的物质和能量交换，并形成公共包层。现今已知的许多激变双星,如新星、X-射线双星、Ia型超新星等等都可能是由相接双星演化而成。 对于相接双星的结构和演化研究,极重要的问题是深入了解和掌握相接双星中的各种复杂物理过程,它对于构造正确的相接双星的演化性质和结局有重大意义。本文在分析了相接双星中的各种物理过程和现有的演化模型的基础上,深入研究了相接双星中的一系列基本问题。这些问题包括产生相接双星的条件、物质交换过程和能量交换过程的关系、相接双星中达到平衡和停止物质和能量交换的条件,外拉格朗日点的质量损失和角动量损失的计算、转动和潮汐效应对双星结构和演化的影响以及理论光变曲线变化性质等等。它们是研究和计算相接双星中各种物理过程的理论基础。我们提出用主、次星表面的平均有效势能大于内拉格朗日点的势能作为产生相接双星的条件,主、次星表面的平均势能不等作为发生物质 交换的条件。由于这些条件都考虑子星自身引力,伴星潮汐力和转动离心力的影响,比原先采用的条件更严格更合理。另外,我们认为物质交换过程和能量交换过程是紧密联系在一起的,物质由一颗子星流到另一颗子星的同时,也携带了相应的能量转移到另一子星上。由于主、次星之间交换质量和能量以及主、次星本身的演化,使次星的势能有可能大于外拉格朗日点L2的势能,从而出现从外拉格朗日点损失物质和角动量,这种新的物质损失形式带走了系统的角动量,对双星的轨道参量及双星结构和演化影响也将是非常显著的。我们还给出了计算外拉格朗日的物质损失和角动量损失以及双星系统轨道参量变化的公式。此外,转动和潮汐效应使子星结构偏离球对称, 从而改变了子星的内部结构,物质交换条件以及使子星内部出现了新的物质运动形式-子午环流,由于子午环流作用,子星内部出现了化学元素和角动量转移。这些都表明研究转动和潮汐效应对双星结构和演化的影响有非常重要的意义。 我们根据以上研究中提出的基本原理,编制了相接双星演化的程序。选择了一个由12M_o和5M_o组成的大质量双星系统作为研究对象,详细比较了有与没有考虑这些物理过程对双星结构和演化的影响。结果证明,这些物理过程对于子星在HR图中的演化轨迹、理论光变曲线而且对系统周期变化以及系统能否维持在相接状态或是突然回转到半相接阶段状态等方面的有显著的影响。说明在相接双星演化模型中应该考虑这些物理过程的影响，同时也应该将相接双星的演化模型建立在严格的数理基础上。 |
| 其他摘要 | More than 50 percent stars are binaries. One special kind of binaries is called contact binaries, which are characterized by the components filling the Roche lobes. By analyzing these complicated physical processes and present models of contact binaries, we study a series of basic problems in this thesis. These problems which include the condition of contact binaries, the relationship of the exchanges of mass and energy and the conditions for starting and stopping of the mass exchange have been discussed in detail. Furthermore, the losses of mass and angular momentum via the outer Lagrange point, the effects of rotation and tide and the variations of theoretical light curves have been investigated and calculated carefully. The condition which the average effective potentials of the two components are greater than that of inner Lagrangian point is adopted as the condition of contact binaries. The mass flows in the common envelope of a contact binary, when the average potential of the primary differs from that of the secondary. These conditions are stricter and more reasonable than the original ones, because the effects of rotation and tide are considered both in the calculations of the potential of the inner Lagrangian point and the average potentials at the surfaces of the components. In addition, the processes of mass transfer and the energy exchange are related to each other closely. When mass flows from one component to the other one, the according energy is transported inevitably. Furthermore, owing to the mass and energy transport and the evolution of the two components, the potential of the secondary may be greater than the one of the outer Lagrangian points. Therefore, the losses of mass and angular momentum via the outer Lagrangian point appear. This new form of the mass loss carries away the angular momentum of the system. So they have an obvious influence on not only the orbital period but also the structure and evolution of the binaries. The formulae of the losses mass and angular momentum via the outer Lagrangian point and calculations of orbital parameters for contact binaries are presented. Besides, due to the rotation and tide, the configurations of the components will deviate from the globe-symmetric structure.Furthermore, there exists a new mass motion in a rotating component, named meridian circulation. The effect of meridian circulation can drive transport of the chemical elements and the angular momentum in a rotating star. According to the above basic principles, we have constructed a modified stellar program of the contact binary. We select a binary system which consists of a 12M$_{\odot}$ star and a 5M$_{\odot}$ star. We conclude that the physical processes mentioned above have obvious influences on not only the evolutive tracks of the components in the HR diagram but also the theoretical light curve. Moreover, the orbital period of the system can also relate to these physical processes. Whether the system keeping still in the contact condition or changing into the semi-detached system suddenly depends on these physical processes, too. The results indicate that we must consider these physical processes in the model of the contact binary and construct the model which is based on the strict mathematic and physical theories. |
| 学科领域 | 天文学
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| 页数 | 87
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| 语种 | 中文
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| 文献类型 | 学位论文
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| 条目标识符 | http://ir.ynao.ac.cn/handle/114a53/5321
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| 专题 | 恒星物理研究组
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推荐引用方式
GB/T 7714 |
宋汉峰. 相接双星的物理过程研究[D]. 北京. 中国科学院研究生院（云南天文台）,2006.
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