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K型密近双星的观测与研究
其他题名Observations and Studies on K-type Close Binaries
刘念平
学位类型博士
导师钱声帮
2014-05-29
学位授予单位中国科学院研究生院(云南天文台)
学位授予地点北京
学位专业天体物理
关键词K型密近双星 相接双星 近相接双星 密近双星形成与演化 O’connell 效应
摘要K型密近双星是具有K型光谱型的密近双星系统。广义来说,这类天体的子星既可能是矮星(主序星), 也有可能是巨星或超巨星等,但后者已经经过主序演化。本文主要研究其中周期较短的对象,它们的子星更接近于矮星。 作者把它们分为两类,相接型和近相接型来进行分析讨论,其中近相接类型包括具有EA和EB两种类型光变曲线的对象。 本文对K型密近双星的研究现状进行了综述,对与之有关的测光和分光方法做了简要介绍;分析了一批实测的K型密近双星样本, 包括六个相接双星样本(从早K型到晚K型)和一个近相接双星样本;对有一定资料的K型密近双星的样本进行了搜集和统计研究。 具体来说,本文研究分析的主要内容和成果如下: 1、通过对相接型样本的测光解轨分析,给出了它们的光变曲线和测光解轨参数(如倾角,质量比等),给出了它们相接度、 几何构型、主次星温度关系等。结果表明,所分析的几个相接型样本都是浅度相接,W次型结构,子星间有一定的温差,从接近零到两百 多K。相接度最小的样本是V1799 Ori,只有3.5\%左右,最大的J0529也只有17\%。J0529的光变曲线与其它样本有明显的区别, 次食是平台食,类似于A次型的光变曲线。该样本的温差最小,次星温度仅仅略高于主星(0$\sim$50 K)。它的质量比不到0.4, 是几个实测样本中最小的。该样本的周期也是最短的,只有0.227天,非常接近于相接双星的截止周期。BI Vul的质量比非常接近于单位1, 且相接度也很低,只有8.7\%,它可能是一个刚刚进入到相接演化阶段的系统。 2、通过对相接型样本的周期分析,发现了周期长期稳定的样本RV CVn。它的周期在近90年间没有明显的长期变化,仅显示出周期 约60年,幅度约0.01天的振荡。其它分析的样本中有三个周期有长期减小,只有V1799 Ori的周期有弱的长期增加。有四个相接双星的周期 表现出周期性振荡,其中V1104 Her有两个周期成分,并且周期满足简单整数比,表明它很可能是两个小质量的伴星天体引起, 并且它们的轨道形成共振,使得外三体系统能保持一定的稳定。 3、对近相接双星DV Psc的分析表明,这是一个极其活跃的系统。系统的测光质量比和分光质量比局地吻合,都在0.7左右。 两子星按势能比计算的填充度大约为86\%(主星)和88\%(次星)。次星的填充比主星的还要略高,说明子星体积比正常 单星要偏大。该样本的光变曲线有很强的不对称性,且存在畸变和快速变化,使得对黑子位型的求解存在很大的不确定性。 该系统较强的表面活动影响了光变曲线的形状,同时影响了对极小时刻的测定。所以作者在进行O-C分析时剔除了 受影响较大的一些时段的数据,从而发现了一个周期接近2.5年,振幅略小于0.001天的周期性变化,以及一个不确定 程度较大的长期增加成分。考虑到测光解得出有较大比例的第三光,该周期性变化可能由一个伴星天体引起,并且伴星天体 的轨道和内双星轨道的夹角可能很大。 4、对40个K型相接双星的统计表明它们几乎都是W次型的浅度相接系统。然而从光变曲线的形状来看,类似于A次型的有4个样本, 不过测光解给出的结果都是W次型。这是首次在相接双星的光谱型上发现整体呈现W次星构型的现象,再次说明了K型(小质量)相接双星 的独特性。作者还发现相接度和质量比呈现一定的相关性,质量比越小,相接度越大,这似乎表明K型相接双星在演化过程中质量比会变小, 同时相接度增加,达到临界的不稳定点之后发生快速的并合。 5、通过样本搜集得到16个近相接型样本,其中EB型样本非常缺失,仅有的3个EB型样本中还有1个光变曲线可能应属于EA型。 这样的结果可能会对TRO理论形成较强的限制。样本中有5个具有半接的构型,包括两个主星充满,三个次型充满,主星充满 的样本周期比次型充满的短。 6、通过样本搜集和统计,发现多数的K型相接双星都表现出O'Connell 效应,这其中大多数为负的O'Connell效应,也有一部分变化的 O'Connell 效应或正的O'Connell 效应。具有这种效应的光变曲线可以利用黑子模型得到较好的拟合。近相接型的对象由于表面活动 强,光变曲线不对称性通常要比相接类型的要明显很多。从样本的结果看,K型近相接双星的大部分为正的O'Connell效应。
其他摘要The K-type close binaries is a category of close binaries with K-type spectra. Broadly speaking, they can be made of dwarf component stars or giant stars. The latter have already finished their main-sequence evolution. This paper mainly discuss the objects with very short periods whose components are mostly similar to dwarf stars. They are divided into the contact type and the near contact type and then discussed. The near contact type consists of EA type and EB type variables in our classification. In this paper, the author presents an overview of the current progress in the research of the K-type close binaries; gives an introduction of the photometric and spectroscopic methods; presents the analysis of a group of observed K-type close binary samples, including six contact samples and one near contact sample; makes a statistic study of the collected K-type close binary samples. The main contents and results are shown as follows. 1. Through photometric solutions of the contact samples, the light curves and the orbital parameters (e.g. inclination and mass ratio ) are derived. The degrees of contact, configurations and temperature relationship are also derived. It is discovered that all of them are shallow contact, W-type systems. The temperature differences between the components of them are about 0 to more than 200 K. The lowest degree of contact is 3.5\% which belongs V1799 Ori, and the highest is 17\% that belongs to J0529. The LCs (light curves) of J0529 are distinctively different from that of other samples. The secondary eclipse of the former is flat, which is similar to that of A-type. Its temperature difference is the smallest, the secondary is only slight hotter than the primary. Its mass ratio is smaller than 0.4, which is the smallest among the analyzed samples. Its period is the shortest, only 0.227 days, which is very close to the cut-off period of contact binaries. The mass ratio of BI Vul is close to the unit 1, and its degree of contact is also low, only 8.7\%, which implies that the object may just evolve into the contact stage. 2. Through period analysis of the contact samples, RV CVn is discovered to keep a long-term stable period. Its period is found to have no obvious change during the past almost 90 years. Only periodic oscillation with period of about 60 years is presented. Three of the rest samples show decreasing periods and only V1799 Ori has a weak increasing period. Four contact binaries are found to show periodic oscillation in their orbital period. Among them ,V1104 Her seems to have two periodic components, which meets the near-integer-ratio. Therefore the most plausible explanation is two stellar companion with small masses in the outer orbits, the orbital resonance helps the outer triple system to keep stable. 3. It is discovered that the near contact binary DV Psc is a highly active system. The photometric mass ratio is locally in agree with the spectroscopic result. Both of them are around 0.7. The fill factors of the two components stars are calculated to be 86\% (primary) and 88\% (secondary). The fill factors of the secondary is a little higher than that of the primary, which indicates that the volume of the secondary may be oversized. The LCs of DV Psc show strong asymmetry, as well as distortion and fast changes, which makes the spot solutions with large uncertainties. The surface activities of the system strongly affect the LCs, thus influence the determination of times of minimum light. Therefore the data which is strongly affected is not used and then a periodic oscillation with a period of close to 2.5 years and a amplitude of close to 0.001 days is found, as well as a uncertain long-term increase. In consideration of a large fraction of a third light in the system, the periodic oscillation may be caused by an additional companion, which may revolve around the binary with a high inclination relative to the binary orbit. 4. From the statistic study of 40 K-type contact binary
学科领域天文学
页数143
语种中文
文献类型学位论文
条目标识符http://ir.ynao.ac.cn/handle/114a53/5982
专题双星与变星研究组
推荐引用方式
GB/T 7714
刘念平. K型密近双星的观测与研究[D]. 北京. 中国科学院研究生院(云南天文台),2014.
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