M型相接双星的搜寻与研究

题名	M型相接双星的搜寻与研究
作者	江林巧
学位类别	博士
答辩日期	2015-07-01
授予单位	中国科学院研究生院
授予地点	北京
导师	钱声帮
关键词	M型密近双星晚K型相接双星测光观测光变分析短周期截止
其他题名	The Search and Study of M-type Contact Binary
学位专业	天体物理
中文摘要	自1967年轨道周期最短的相接双星CC Com被发现后近半个世纪的时间里，W UMa型双星的轨道周期分布就一直在0.22天附近存在尖锐的短周期截止，即观测上相接双星存在一个0.22天左右的最短周期，且一直没有发现M型相接双星的存在。近年来随着各类巡天项目如火如荼的开展，一大批轨道周期位于0.22 天附近的相接双星候选体被陆续发现。本论文依托SDSS和SuperWASP巡天发现的短周期相接双星候选体表，对部分样本进行了后续详细的测光观测研究，其中包括2个M型相接双星样本和3个晚K型相接双星样本。同时，我们还搜集了文献中目前已经发表的所有轨道周期位于0.22天附近的相接双星样本，结合本论文得到的结果进行了统计研究。具体来说，得到如下的研究成果： 1、对SDSS巡天中发现的M型相接双星候选体SDSS J001641-000925和SDSS J012119.10-001949.9分别进行了轨道周期变化分析和光变曲线解轨分析。轨道周期分析的结果表明SDSS J001641-000925的O ? C曲线呈现出周期5.7年、变幅为3.7分钟的周期性变化，这个周期性变化很可能是由一个质量约为0:14M⊙的红矮星第三天体的光时轨道引起。这说明SDSS J001641-000925是一颗稳定的红矮星相接双星系统，系统的轨道不存在快速的收缩。而光变曲线分析的结果显示SDSS J012119.10-001949.9 是一颗中等质量比的浅度相接双星，系统总光度有相当一部分来自第三光的贡献，且第三光的贡献比例向长波端增大。这说明该系统很可能也是一个三星系统，第三光来自一个冷的伴星天体。 2、对SuperWASP巡天中发现的两颗晚K型相接双星候选体1SWASP J074658.62+224448.5和1SWASP J075102.16+342405.3的光变曲线和轨道周期变化都进行了分析研究。结果表明，1SWASP J074658.62+224448.5是一颗小质量比的浅度相接双星系统，而1SWASP J075102.16+342405.3却是一颗大质量比的深度相接双星系统。同时，对这两个系统轨道周期分析的结果都表明它们的轨道周期都在以10?7dyr?1的速率快速增加。由于这样快的轨道周期增加率对应着非常大的质量转移率，这对两个小质量晚型双星系统来说几乎不可能。因此，我们偏向于认为这两个系统的O ? C曲线向上的抛物线变化都是第三天体的光时轨道效应引起的周期性变化的一部分，即这两个系统很可能也是三星系统。 3、对SuperWASP巡天发现的另一颗晚K型相接双星候选体1SWASP J024148.62+372848.3的光变曲线和轨道周期进行了分析研究。由于可用于轨道周期分析的数据非常弥散，得到的O ? C曲线暂时没有表现出明显的变化趋势。而光变曲线分析的结果表明1SWASP J024148.62+372848.3是一颗大质量比的中度相接双星系统，且系统的两子星表面覆盖大量黑子。测光解还显示第三光对系统总光度的贡献高达40%，而表面温度略高的主星对系统总光度的贡献却比次星还小，这可能是由于主星表面黑子覆盖率远大于次。因此我们认为1SWASP J024148.62+372848.3很可能也是一个三星系统，但由于系统的两子星表面被大面积的黑子覆盖，导致第三光对系统总光度的贡献相对增大。 4、我们统计了目前已经发现并证实的所有位于短周期截止附近的相接双星样本，共计20个样本，其中包括5个M型和15个晚K型。结果显示，大部分相接双星都是具有中等或偏大质量比的浅度相接系统。高达75%的样本有证据证明第三天体的存在，剩下几个系统也有间接的证据表明它们很可能也是三星系统，这表明第三天体确实普遍存在于晚型相接双星系统中。这些样本的光变曲线普遍存在明显的不对称，再次说明这类晚型密近双星系统确实都非常活跃，两子星表面很可能存在强磁场和剧烈的磁活动。
英文摘要	From the discovery of CC Com in 1967, which has the shortest period among contact binaries, during nearly half a century, contact binaries of W UMa type show a very well-defined short-period cut-off at about 0.22 days. This means, observationally, contact binaries have a shortest-period at 0.22 days, and no Mtype contact binaries have been found during this period. However, the advent of large-scale photometric surveys have led to the discovery of large number of contact binaries candidates with periods around 0.22 days. In this paper, based on the short-period contact binaries candidates found by the SDSS and SuperWASP, we present the follow-up detailed photometric studies of some samples, including two M-type contact binaries candidates and three late K-type contact binaries candidates. Meanwhile, we have collected all the well-studied contact binaries that have periods around 0.22 days, combined the results this paper obtained to conduct a statistical study. Specifically, the results are obtained as follows: 1. The period change study and the light curves analysis for the M-type contact binary candidates SDSS J001641-000925 and SDSS J012119.10-001949.9 are presented respectively. The period change study suggests that the observed minus calculated (O?C) diagram shows a cyclic oscillation with an amplitude of 0.00255 days and a period of 5.7 yr. The cyclic variation can be explained by the light travel time effect via the presence of a cool stellar companion with a mass of 0.14 M⊙. These results reveal that SDSS J001641-000925 is the first stable red dwarf contact binary, while the rapid decrease in the orbital period is not true. The light curve analysis of SDSS J012119.10-001949.9 suggests that the binary is in contact configuration with a moderate mass ratio. A third light contributing parts of the total luminosity was found, and the contribution of monochromatic third light increases with wavelength. This indicates that J012119.10-001949.9 is a triple system, and the third light comes from an additional cool component. 2. We present the first photometric study and the period change analysis of two late K-type contact binary candidates 1SWASP J074658.62+224448.5 and 1SWASP J075102.16+342405.3. It is found that 1SWASP J074658.62+224448.5 is a shallow contact system with a low mass ratio, while 1SWASP J075102.16+342405.3 is a deep overcontact system with a high mass ratio. The period change analysis suggests that the orbital period of both systems are undergoing increase at a rate of 10?7d.yr?1. Since this high rates of period change corresponds to very a large mass transfer rates, which may be physically impossible, we prefer to deem that the period increases of both systems are part of the cyclic variations due to the presence of a tertiary component, which means that these two systems may be triple systems. 3. Another late K-type contact binary candidate 1SWASP J024148.62+372848.3 was also studied with light curves solutions and period change analysis. Due to the large spread of the data used in the period analysis, the O?C curve is not enough to reveal any variations. The light curves solutions suggest that 1SWASP J024148.62+372848.3 is a middle contact system with a high mass ratio, and the two components are found to have large dark-spot coverage. The solutions also show that the third light contributes about 40% of the total luminosity, while the component with higher temperature contributes less luminosity than the component with lower temperature, this may be caused by the larger dark-spot coverage of the component with higher temperature. So, we deem that 1SWASP J024148.62+372848.3 may be a triple system, and due to the large dark-spot coverage of the two components, the contribution of the third light are relatively increased. 4. We have collected all the well-studied contact binaries that have periods less than 0.23 days. A total of twenty contact binaries were obtained, including five M-type and fifteen late K-type. It was found that most of contact binary systems are in shallow contact. More than 75% systems have evidences to proof that the third component exists in these systems, and others have circumstantial evidences to indicate it may be a triple systems. This suggests that the third components are ubiquitous in late-type close binary systems. The light curves of most of these samples show obvious asymmetry, this again signs that these late type close binaries are very active, the surfaces of the two components may exist strong magnetic field and intense magnetic activities.
语种	中文
学科主题	天文学
公开日期	2016-06-01
内容类型	学位论文
源URL	[http://ir.ynao.ac.cn/handle/114a53/9466]
专题	云南天文台_双星与变星研究组
作者单位	中国科学院云南天文台
推荐引用方式 GB/T 7714	江林巧. M型相接双星的搜寻与研究[D]. 北京. 中国科学院研究生院. 2015.