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Alternative TitleStudy and Discussion on Period of Algol-type Binary and Structure Equations of Binary
Thesis Advisor钱声帮
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
KeywordAlgol型双星 双星结构 轨道周期
AbstractAlgol型双星作为双星的一类,由于它的光变显著而成为观测历史最长的食双星。长期光变极小时刻的观测积累了大量的观测资料,这使得人们能够了解某个源上百年的轨道周期变化,为研究与之相关的物理机制提供了极好的条件。 本文简述了Algol型双星的基本特性;周期变化的种类;周期分析的数学方法;导致周期变化的各种可能的原因及相关的计算公式。简单介绍并探讨了双星的结构方程,讨论了同步转动的假设下双星结构的一维化问题和双星演化过程中每“层”物质角动量守恒的问题。利用位力定理给出了角速度的表达式并重新书写了能量平衡方程。对两颗Algol 型样本星(UW Vir和VW Hya)进行了周期分析并取得成果如下: 1.对Algol型双星UW Vir进行了周期分析,在收集了所有可能得到的光极小时刻资料后,发现该星的轨道周期存在长期的快速增加,增加率dP/dt=+1.37(0.01)*10-6天/年,同时含有振幅为0.0397天和周期为62.3年的周期性变化。轨道周期的快速增加可能是次星到主星得物质流引起的。严格的周期性变化表明很可能存在一个质量大于0.94Msun的第三天体,然而测光观测上又没有发现第三天体的任何信息,说明它可能是一颗致密天体。 2.基于我们观测得到的Algol型双星VW Hya的一个极小时刻点和收集到的其它极小时刻资料,对该双星的轨道周期进行了分析,发现轨道周期在长期增加:dP/dt=+6.34(\.89)*10-7天/年。除此之外,还叠加了两个周期性变化,周期和振幅分别为51.5年、0.0639天和8.75年、0.0048天。周期增加可用次星到主星7.89*10-8Msun/年的物质流来解释。两个周期性变化表明该系统中可能存在质量分别大于2.84Msun和0.53Msun的额外天体。且质量大于2.84Msun的额外天体可能是个看不见的中子星或黑洞候选体。
Other AbstractAlgol-type binary, as a subclass of binary, bears long time observation for its distinguished light curves. Long time observations of times of light minimum accumulate lots of information of Algol binaries. So we can recognize the variation of orbit period up to hundreds of years. This makes it a very good source to understand the corresponding physical mechanisms. In the present paper, the basic properties of Algol-type binary, the sorts of orbit period variation, corresponding mathmatic methods, the pysical mechanisms of period variation, are reviewed briefly. The structure equations of binary are studied also, the problem of structure can be viewed as one dimension in high approximation given the assumption of uniform rotation was discussed. The conservation of angular momentum of every layer of stellar mass was discussed. With the help of Virial theorem, the formula of angular velocity is deduced, and ennergy equilibrium equation is rewrited. Two Algol-type binaries(UW Vir and VW Hya) were studied based on the analyses of their O-C diagram, the variations of the orbital periods of them are obtained as follows: 1. The orbit period variation of Algol type binary UW Vir was analyzed. After collecting all possible times of light minimums, a continuous increase of orbit period was discovered at a rate of dP/dt=+1.37(\.01)*10-6days/year while it undergoes a cyclic period change with amplitude of 0.0397 days and a period of 62.3 years. The continuous increase of orbit period may be caused by a conservative mass transfer from less massive component to more massive one. Sinusoidal period oscillation indicates a third body with mass greater than 0.94Msun. Since no observational informations were reported about the third body, it may be a compactobject. 2. Base on the times of light minimum of Algol type binary VW Hya observed and collected, the orbit period of the binary is analyzed. It is discovered that the orbit period shows a continuous increase at a rate of dP/dt=+6.34(0.89)*10-7 days/year.Meanwhile, two period oscillations, with periods and amplitudes of 51.5 years, 0.0639 days and 8.75 year, 0.0048 days, respectively, were discovered. A conservative mass transfer from the less massive component to the more massive one at a rate of 7.89*10-8 Msun/year may be the reason that produce the period increation. The period oscillation may indicate two additional bodies with mass larger than 2.84Msunand 0.53Msunrespectively, and the more massive one may be a unseen neutron star or black hole candidate.
Subject Area天文学
Document Type学位论文
Recommended Citation
GB/T 7714
张嘉. Algol型双星的周期分析和双星结构方程讨论[D]. 北京. 中国科学院研究生院(云南天文台),2008.
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