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密近双星BH Cassiopeiae的光学与X射线研究
Alternative TitleAn optical and X-ray study of the contact binary,BH Cassiopeiae
Thesis Advisor艾力·伊沙木丁
Degree Grantor中国科学院大学
Place of Conferral北京
Degree Name理学硕士
Degree Discipline天体物理
Keyword变星,食双星,光谱,X射线 stars:variables,binaries:eclipsing,binaries:spectroscopic,X-ray:binaries
AbstractWUMa型相接双星是一种两颗子星均充满洛希瓣的相互作用双星。该类双星的重要特征为外部可能由公共包层包裹,两颗子星温度差别较小,在光度观测上光变曲线呈现连续变化的特征。该类双星发生着复杂的物理过程,包括复杂的物质交流、能量转移,引力与辐射交流,光球层活动及X射线辐射等。为了对这类双星进行研究,我们选择了一颗名为BH Cassiopeiae的WUMa型相接双星作为研究对象。 2017年及2018年我们利用南山1米望远镜观测获得WUMa型相接双星BHCas的高质量CCD时域数据。通过将我们新得到的极小时刻数据与文献中的历史数据相结合,我们发现BHCas的轨道周期呈现出一个长期增加的趋势,我们得到轨道周期的变化率为dP/dt=+3.27×10E(-7)dyrE(-1),这可能是由于从质量小的子星向质量大的子星转移角动量造成的。在这个长期增加的趋势上叠加了至少一个周期震荡(A'=0.00300 days和P”=20.09yrs),该震荡可能是由额外天体围绕BHCas造成的。在2018年和2019年,我们使用兴隆2.16米望远镜观测得到了BHCas在0.0相位和0.5相位的低分辨率光谱,在这两个相位处的光谱分别对应K3V±1和G8V±2的光谱型。根据光变曲线拟合的解轨结果和不同相位处子星的光度贡献的分析,我们推断主星的光谱型很有可能是K3V±1。我们通过引入黑子模型拟合光变曲线中出现的不对称现象,获得了良好的拟合结果。 另外,次星上黑子位置、温度和面积的逐月变化暗示出BHCas 次星的磁场活动比主星更加活跃。这种活跃的黑子活动和光学耀斑是第一次在WUMa系统中被观测到。使用2003年和2012年XXM-Newton对BHCas的观测数据,我们得到了BHCas的X射线光变曲线和光谱,该光谱能够很好地被黑体或韧致辐射模型拟合。BHCas的软X射线流量的范围约为8.8-9.7×10E(30)ergsE(-1)。
Other AbstractWUMa type binary star is a type of interaction binary star with two components filling their Roche lobe. The important feature of this kind of binary star is that the outer part of the binary star may be wrapped by a common envelop. Complex physical processes occur in such binary stars, including complex material exchange, energy transfer, gravitational and radiation exchange, photospheric activity and X-ray radiation. In order to study this kind of binary star,a W UMa type binary star named BH Cassiopeiae was selected. We present the revised and high quality CCD time series observations in 2017 and 2018 of the W UMa-type contact binary BH Cas. The combination of our new determinations of minimum times and those collected from the literatures reveal a long-term period increase with a rate of dP/dt =+3.27×10E-7dyrE-l, which can be accounted for by angular momentum transfer as the less-massive component loses its mass to the more massive one. At least one cyclical oscillation (A'=0.00300 days and P"=20.09 yrs) superimposed on the long-term period increase tendency is attributed to one additional object that orbits BH Cas. The low-resolution spectra of this source are observed at phase~0.0 and~0.5 in 2018 and 2019, and the spectral types are identified as K3V±1 and G8V±2. According to the solution of light curve fitting and the luminosity conributions at different phases, the spectral type of the primary star is most likely K3V±1. We infer a cool spot on the hotter and less-massive component to fit the asymmetry of light curves. In addition, month over month changes in the location, temperature, and area of spots on the secondary star in different observations may indicate that the magnetic field activity of the secondary is more active than that of the primary. Such strong spot activities and optical flare are both detected at the same time from a W UMa-type star for the first time. With the .X2MM-Newton observations taken in 2003 and 2012, the X-ray light curve is obtained and the X-ray spectra can be well described with a blackbody or a bremsstrahlung model. The soft X-ray luminosity of BH Cas is estimated as 8.8-9.7×10E30ergsE-1.
Document Type学位论文
First Author AffilicationXinjiang Astronomical Observatory, Chinese Academy of Sciences
Recommended Citation
GB/T 7714
刘军辉. 密近双星BH Cassiopeiae的光学与X射线研究[D]. 北京. 中国科学院大学,2019.
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