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亮蓝变星的光变起因和星风结构
Alternative TitleThe irregular photometric variations and the structure of wind of LBVs
郭建恒
Subtype博士
Thesis Advisor李焱
2006-06-13
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大质量恒星 演化 亮蓝变星 连续谱 星风
Abstract亮蓝变星是具有不规则光变的大质量恒星,它们的光变起因一直不为人们所知。针对它们特殊的性质,星风成为探索亮蓝变星光变机制的最好工具。在本文中我们将主要研究它们的星风,在结合了前人对其测光、光谱和偏振等性质后,我们着重研究了它们的连续谱。在考虑大气模型并结合星风的影响后,我们发现亮蓝变星的光变不可能是由于单纯的物质损失率的增加而形成的,它们的光变一定与其自身的膨胀/收缩有关。同时,在通过连续谱的拟合后我们发现,亮蓝变星的星风结构与其所处的状态密切相关。当它们处在最小状态时,它们的星风与正常的B型星相似,星风的加速是快的、陡峭的(β<1)。当它们处在最大状态时,它们的星风与正常的A型星相似,星风的加速是慢的、平坦的(β>1)。对于亮蓝变星星风的几何结构,我们认为一个球状的星风已经可以很好的说明观测的性质,那些观测到的偏振现象很可能是因为星风的不均匀性而引起的,星风中的“团”是诱发偏振的主要原因。 另外,针对两颗具有双峰结构特征的亮蓝变星,我们认为它们的双峰结构最有可能是因为光学“伴星”污染所致,它们可能与其他亮蓝变星并无本质的不同,所有亮蓝变星的内在性质是一致的。
Other AbstractLuminous Blue Variables are evolutionary massive stars. Their most distinct characteristic is irregular light variations at different timescales. Up to now these models for explanting the phenomenon are not successful. In fact we even don’t know basic physic parameters of some LBVs. Combine the spectra of IUE with photometric data Models for the continua of luminous blue variables in minimum and maximum states are calculated. We found that the mass-loss increase by itself cannot account for the decrease of the effective temperature. The increase of the mass loss rate causes only a comparatively small change in the radius of continuum formation. The observed light variations could be induced from deeper stellar envelope. In addition, via fitted the continua of LBVs we may determine the properties of the wind. We found that the velocity gradient of winds of LBVs is stepper in the minimum phase. The exponent (β) of the wind velocity equals 0.5 and more than 1 in the minimum and maximum state, respectively. We determine also the geometry of the wind. A spherical wind may reproduce the observed continua. These observed polarizations, which are variable in both strength and position angle, could hint that the localized density enhancements, or `clumps' could be exist in the base of the wind. For R 110 and R 127 both show two peaks in the continua. We consider that the continua of both stars could be “contaminated” by optical companion. All LBVs display evidence for intrinsic uniformity.
Subject Area天文学
Pages112
Language中文
Document Type学位论文
Identifierhttp://ir.ynao.ac.cn/handle/114a53/5320
Collection恒星物理研究组
Recommended Citation
GB/T 7714
郭建恒. 亮蓝变星的光变起因和星风结构[D]. 北京. 中国科学院研究生院(云南天文台),2006.
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