YNAO OpenIR  > 大样本恒星演化研究组
W UMa型相接双星的形成和演化
姜登凯
Subtype博士
Thesis Advisor王建成 ; 李立芳
2010-05-27
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
Keywordw Uma型相接双星 演化 不稳定性 旋转
AbstractW Ursae Majoris (W UMa) 型相接双星是两子星均充满洛希临界面的一类双星。两子星共同分享一个公共包层,并且它们的表面温度几乎相等,展示出EW型光变曲线。根据133颗W UMa型相接双星的样本,我们研究了W UMa型相接双星的能量转移及其对次星的影响。另外,我们利用Eggleton恒星演化程序,研究了不同主星质量的W UMa型相接双星的最小质量比。我们还计算了由并合形成的单星的自转速度,并研究了W UMa型相接双星并合过程中的质量损失。取得了如下的研究成果:1. 我们给出了W UMa型相接双星的相对能量转移率(U1,U2)与质量比的关系,其中,U1是转移光度与主星表面光度的比值,U2是转移光度与次星核反应光度的比值。通过假设两子星刚好充满内洛希临界面并且表面有效温度相等,以及主星为零龄主序星(ZAMS),我们得到了理论曲线(U1-q,U2-q)。尽管这 些理论曲线可以反映观测系统的U1-q和U2-q的分布情况,但有些观测系统明显偏离这些理论曲线。这主要是由于W UMa型相接双星的两子星的温度不相等造成的。2. 次星的半径与密度都与相对能量转移率U2相关,U2越大,次星膨胀的越厉害,密度越小。同时,我们还发现,两子星的相对温度差与U1 相关,U1越大,主次星的相对温度差越小,这表明两子星之间可能存在热耦合,当W UMa型相 接双星分为A次型和W次型时,会依赖于主星转移给次星的能量。另外,主次星的相对温度差与主星质量之间不存在相关性,这就表明公共包层的性质(对流或辐射)对两子星之间的能量转移并没有明显的影响。3. 我们发现当主星质量小于1.3Msun时,W UMa型相接双星的最小质量比随着主星质量的增加而减小,当主星质量大于1.3Msun时,最小质量比几乎为常数。我们通过比较观测样本和理论最小质量比后发现主星的无量纲回旋半径,即主星的结构在研究最小质量比时非常重要,它对决定相接双星的动力学稳定性起关键作用。4. 我们的研究发现:如果W UMa型相接双星的并合过程中质量和角动量守恒,那么并合形成的单星的赤道自转速度大约为588>819 km/s,这一速度远大于其破裂速度(vb)。这就表明要么并合后形成的单星显著膨胀(其半径为并合前主星半径的3.7>5.3倍),要么在并合过程中损失大量的质量(系统总质量的21%~33%)和角动量。如果考虑磁滞作用的影响,损失的质量会减小到系统总质量的12%~18%。W UMa型相接双星在并合过程中损失大量的物质和角动量,可能是由于次星轨道能在公共包层中释放造成的。
Other AbstractW Ursae Majoris (W UMa) contact binaries are eclipsing variables in which two components are in contact or over°owing their Roche limiting surfaces. Two components ofWUMa contact binaries share a common convective envelope,and their effective temperature are nearly identical. Therefore,WUMa binaries show EW-type light curves. Based on the physical parameters of 133 W UMa contact binaries, the energy transfer and its effects on the secondaries in W UMa contact binaries are investigated. In addition, using Eggleton's stellar evolution code, we study the minimum mass ratio (qmin) of W UMa contact binaries under the different primary masses. We also investigate the mass loss during the merging process of W UMa-type systems and calculate the rotation cities of the single stars formed by the merger of W UMa contact binaries due to tidal instability. some results are obtained as the follows: 1. Relations between the mass ratio (q) for W UMa contact binaries and the relative energy transfer rates(i.e. U1, the ratio of the transferred luminosity to the surface luminosity of the primary and U2, the ratio of the transferred luminosity to the nuclear luminosity of the secondary)are given . The theoretical curves (U1-q and U2-q) are derived based on the various assumptions, such as two components in each W UMa system are nearly identical in effective temperature, they just ¯ll their inner Roche lobes, and the primaries are zero-age main sequence (ZAMS)stars. Although these curves can reflect the distribution of U1-q and
Subject Area天文学
Pages100
Language中文
Document Type学位论文
Identifierhttp://ir.ynao.ac.cn/handle/114a53/4660
Collection大样本恒星演化研究组
Recommended Citation
GB/T 7714
姜登凯. W UMa型相接双星的形成和演化[D]. 北京. 中国科学院研究生院(云南天文台),2010.
Files in This Item:
File Name/Size DocType Version Access License
W UMa型相接双星的形成和演化.pdf(21487KB)学位论文 开放获取CC BY-NC-SAView Application Full Text
Related Services
Recommend this item
Bookmark
Usage statistics
Export to Endnote
Google Scholar
Similar articles in Google Scholar
[姜登凯]'s Articles
Baidu academic
Similar articles in Baidu academic
[姜登凯]'s Articles
Bing Scholar
Similar articles in Bing Scholar
[姜登凯]'s Articles
Terms of Use
No data!
Social Bookmark/Share
File name: W UMa型相接双星的形成和演化.pdf
Format: Adobe PDF
All comments (0)
No comment.
 

Items in the repository are protected by copyright, with all rights reserved, unless otherwise indicated.