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1.
刘亮 《天文学报》2013,54(1):82-84
大熊W型相接双星是两颗子星均充满并溢出各自洛希瓣、具有对流公共包层的双星系统.相接双星中存在各种各样的相互作用,给理论模型带来许多可变参量,对理论研究提出了挑战.上世纪六七十年代,经过激烈的争论,相接双星的对流公共包层模型得到公认,相接双星的热弛豫震荡模型、相接不连续模型及角动量损失理论相继被提出.然而,在过去的近40 yr中,理论研究似乎遇到了瓶颈.大量未知参量的共存,使相接双星的理论研究难以进一步开展.研究相接双星的聚星、星团环境,能为相接双星的形成和演化提供丰富的信息,因而是探索相接双星演化问题潜在的生长点.越来越多的观测证据表明,大量相接双星存在于聚星系统或者星团当中.作为母系统的聚星、星团为研究其中的相接双星提供了丰富的演化信息.本文针对这些重要天体系统中的相接双星进行了成员认证、测光观测、周期分析和基本物理参量求解等多项研究,同时对相接双星研究的现状做了简要概述.主要成果如下:  相似文献   

2.
1．分析光变亮度极小时间食双星仙后座V1107是典型的大熊座W型短周期食变双星,图1为它在一个周期内观测得到的光变曲线,可见一个主极小和一个次极小。  相似文献   

3.
半相接双星室女座UW轨道周期变化的物理机制研究   总被引：1，自引：0，他引：1  
对大陵五型半相接双星室女座UW的轨道周期变化进行了分析.结果表明该星的轨道周期在长期快速增加(dP/dt=+1.37×10-6天/年)的同时也含有周期为62.3年的周期性变化.利用Brancewicz和Dworak在1980年给出的基本物理参量,对引起轨道周期变化的物理机制进行了分析研究.分析表明一个质量为Ms>0.94M⊙的第三天体的光时轨道效应能对轨道周期的周期性变化成份作出解释.由于在观测上没有发现这个第三天体存在的信息,它有可能是一个致密天体(如白矮星等).轨道周期的长期增加成份可解释为由次星到主星的物质交流引起(dM2/dt=1.43×10-7M⊙/年),这与该系统次星充满的半接几何结构是相一致的.但是,根据双星演化理沦,大陵五型半相接双星应该处于以次星的核反应时标进行物质交换的慢速物质交流演化阶段,而分析发现该星的轨道周期变化时标远小于次星的核反应时标,但接近于次星的热力学时标,揭示了(1)这颗双星处于以次星热力学时标进行物质交换的快速物质交流演化阶段;或(2)系统的星周物质要通过角动量交换对轨道周期的快速增加做贡献.  相似文献   

4.
本文回顾了W UMa型相接双星观测和理论研究的历史。总结了W UMa型相接双星观测特性和理论研究的成果。最后讨论了W UMa型相接双星理论模型研究中存在的问题及其解决这些问题的一些可行方法。  相似文献   

5.
张瑞玉  李焱 《天文学报》2012,53(4):274-290
通过计算双星演化中的角动量转移,研究了潮汐作用下双星系统自转与公转周期的变化以及潮汐作用对双星演化的影响.结果表明,密近双星系统在主序演化时,潮汐摩擦会在较短的时间内使自转与公转达到比较接近的状态,此后经过一个较长时间的调整才能使自转与公转达到同步转动.物质交换阶段开始后,半相接双星系统更容易出现非同步转动,而相接双星系统物质交换很难破坏系统的同步状态.同时比较了非同步双星模型与同步双星模型演化曲线在赫罗图上的不同,结果表明非同步模型在物质交换阶段主星演化曲线向赫罗图光度和有效温度高的方向移动.最后通过对统计的观测数据进行分析后发现,采用该模型可以解释观测上双星超过潮汐锁定时标后仍然存在非同步转动的现象.  相似文献   

6.
计算了总质量为3.9M,具有不同初始质比和两子星间距的一组模型在总质量、总角动量守恒假设下的Case A演化,以探求Case A演化与几乎相接双星(NCS)可能的联系.结果表明确实存在经过Case A质量交流演化为NCS系统的途径。并且这样形成的NCS系统其随后的演化有两种前景:一种随即演化为相接系统;另一种则经由慢速质量交流成为较稳定的半接或不接系统.但能够演化为NCS状态的初始模型范围极为狭窄,本文大致确定了它们的初始质比、子星间距等参量范围. 结合模型计算结果,对已知29个NCS系统作了统计研究,结果表明NCS系统与相接双星在演化上有很密切的联系.  相似文献   

7.
GM Boo是一个已经被发现超过10年的短周期(约0.36天)相接双星。获得了GM Boo在2010到2015年新观测的多波段时序测光数据及其低色散光谱。从光变曲线中提取了19个新的光变极小时刻,并结合历史数据推导出该双星轨道周期增长速率d P/dt=1.06×10~(-7)d·y r~(-1)。Wilson-Devinney程序被用来分析GM Boo的测光轨道解。得出它是一个典型的W次型的过相接双星系统,其质量比约为q~1.22,相接度约为f~11%。模型中添加了2个黑子拟合不对称的光变曲线,说明此系统具有较强的活动性。  相似文献   

8.
本文提出了判断双星自转同步性的一种新方法．把假定双星为同步自转时的拱线进动周期的理论计算值与该双星的观测值之比作为同步自转参量,以判断双星同步自转情况．利用此方法对ＹＣｙｇ和ＣＷＣｅｐ两对双星系统中子星同步自转情况做了判断．结果表明,其中ＣＷＣｅｐ为同步自转双星,ＹＣｙｇ为接近同步自转双星．最后将所得结果与其他作者用直接测量自转速度方法所得的结果进行比较,结果符合得很好  相似文献   

9.
本提出了判断双星自转同步性的一种新方法,把假定双星为同步自转时的拱线进行周期的理论计算值与该双星的观测值之比作为同步自转参量,以判断双星同步自转情况,利用此方法对ＹＣｙｇ和ＣＷＣｅｐ两对双星系统中子星同步自转情况做了判断。结果其中ＣＷＣｅｐ为同步自转双星,ＹＣｙｇ为接近同步自转双星,最后将所得结果与其他作用用直接测量自转速速度方法所得的结果进行比较,结果符合得很好。  相似文献   

10.
我们对前文（Ⅰ）和（Ⅱ）的实测和计算结果进行了统计分析，讨论了自转同步与相对半径、轨道周期间的关系．结果表明：几乎所有r＞0．18的不相接双星系统子星都是同步的，而r＜0．10的子星均处于非同步自转．在相接、半相接双星系统中，同步性与相对半径r也有很好的相关性，但由于子星间物质交流的影响，它们的同步性临界相对半径为0．21，大于不相接双星系统的0.18．  相似文献   

11.
A theoretical model for explaining the O‘Connell effect of close binary stars is given based on the hypothesis that the circumstellar material of a binary system is captured by its components.The results inferred form the model suggest that late-type and /or short-period binaries can easily produce obvious O‘Connell effect and that the occurrence of O‘Connell effect has no relation with the type of binaries,These conclusions are in agreement with the observed results.The observed O‘Connell effects of six binary systems are examined by the model.For three W-subtype W UMa binaries(YY Eri,BX Per and SW Lac).the densities of the materials captured by the two components are assumed to be equal,and the calculated O‘Connell effect is found to be almost equal to the observed effect.For three A-subtype W UMa systems(CN And,FG Hya and AU Ser),the two densities are assumed to be different,and are calculated separately.The calculated O‘Connell effect turns out to agree better with the observed effect than that was formerly obtained.  相似文献   

12.
B andV light curves for one epoch and radial velocity curves of three different epochs have been analyzed to revise the solution of TX UMa. The solution has been adjusted simultaneously in the light curves and radial velocity curves by the method of Wilson and Devinney's differential correction. The primary star's surface rotation rate to synchronous rate is determined as 1.768 from one of the radial velocity curves. The absolute dimension of the system has been deduced based on the simultaneous solution. The primary star is well fitted to the evolutionary track for a single star while the secondary star, while filling its Roche lobe, is fitted to the evolutionary track for a close binary system.  相似文献   

13.
Orbital period changes of ten contact binary systems (S Ant, ε CrA, EF Dra, UZ Leo, XZ Leo, TY Men, V566 Oph, TY Pup, RZ Tau and AG Vir) are studied based on the analysis of their     curves. It is discovered that the periods of the six systems, S Ant, ε CrA, EF Dra, XZ Leo, TY Men and TY Pup, show secular increases. For UZ Leo, its secular period increase rate is revised. For the three systems, V566 Oph, RZ Tau and AG Vir, weak evidence is presented that a periodic oscillation (with periods of 20.4, 28.5 and 40.9 yr respectively) is superimposed on a secular period increase. The cyclic period changes can be explained by the presence of an unseen third body in the three systems. All the sample stars studied are contact binaries with     .
Furthermore, orbital period changes of 27 hot contact binaries have been checked. It is found that, apart from AW UMa with the lowest mass ratio     , none shows an orbital period decrease. The relatively weak magnetic activity in the hotter contact binaries means little angular momentum loss (AML) from the systems via magnetic stellar winds. The period increases of these W UMa binaries can be explained by mass transfer from the secondary to the primary components, which is in agreement with the prediction of the thermal relaxation oscillation (TRO) models. This suggests that the evolution of a hotter W UMa star is mainly controlled by TRO. On the other hand, for a cooler W UMa star     , its evolution may be TRO plus AML, which coincides with the recent results of Qian.  相似文献   

14.
Contact binaries consist of two strongly interacting component stars where they are filling their critical Roche lobes and sharing a common envelope. Most of them are main-sequence stars, but some of them are post main-sequence systems. They are good astrophysical laboratories for studying several problems such as the merging of binary stars, evolution of the common envelope, the origin of luminous red nova outbursts and the formation of rapidly rotating single stars with possible planetary systems. A large number of contact binary candidates were detected by several photometric surveys around the world and many of them were observed by the LAMOST spectroscopic survey. Based on follow-up observations,the evolutionary states and geometrical structures of some systems were understood well. In this review,we will introduce and catalog new stellar atmospheric parameters(i.e., the effective temperature(Teff), the gravitational acceleration(log(g)), metallicity([Fe/H]) and radial velocity(Vr)) for 9149 EW-type contact binaries that were obtained based on low-and medium-resolution spectroscopic surveys of LAMOST. Then we will focus on several groups of contact binary stars, i.e., marginal contact binary systems, deep and low-mass ratio contact binary stars, binary systems below the short-period limit of contact binaries and evolved contact binaries. Marginal contact binaries are at the beginning of the contact stage, while deep and low-mass ratio contact binary stars are at the final evolutionary stage of tidally locked binaries. Several statistical relations including the period-temperature relation are determined well by applying LAMOST data and their formation and evolutionary states are reviewed. The period-color relation of M-type binaries reveals that there are contact binaries below the short-period limit. Searching for and investigating contact binaries near and below this limit will help us to understand the formation of contact binary systems and a new prediction for the short-period limit is about 0.15 d. Some evolved contact binaries were detected by the LAMOST survey where both components are sub-giants or giants. They provide a good opportunity to investigate evolution of the common envelope and are the progenitors of luminous red novae like V1309 Sco.  相似文献   

15.
We present the results of our study of the eclipsing binary systems CSS J112237.1+395219,LINEAR 1286561 and LINEAR 2602707 based on new CCD B, V, Rcand Iccomplete light curves. The ultra-short period nature of these stars, as reported by Drake et al., is confirmed and the system's periods are revised. The light curves were modeled using the 2003 version of the Wilson-Devinney code. When necessary, cool spots on the surface of the primary component were introduced to account for asymmetries in the light curves. As a result, we found that CSS J112237.1+395219 is a W UMa type contact binary system belonging to W subclass with a mass ratio of q = 1.61 and a shallow degree of contact of 14.8%where the primary component is hotter than the secondary one by 500 K. LINEAR 1286561 and LINEAR2602707 are detached binary systems with mass ratios q = 3.467 and q = 0.987 respectively. These detached systems are low-mass M-type eclipsing binaries with similar temperatures. The marginal contact,fill-out factor and temperature difference between components of CSS J112237.1+395219 suggest that this system may be at a key evolutionary state predicted by thermal relaxation oscillation(TRO) theory. From the estimated absolute parameters, we conclude that our systems share common properties with other ultrashort period binaries.  相似文献   

16.
The aim of this work is to study the gravity and the effective temperature distribution on the outer equipotential surface of a contact binary. In particular, the lines of constant g, (the iso‐g curves), are computed and plotted on the outer surface Cs of contact configurations. Since the gravity distribution would also specify the effective temperature distribution on the binary's common photosphere through the gravity darkening effect, these lines correspond to isothermals too. Applications have been made to two contact binaries; namely, to AW UMa and OO Aql, two systems with very different mass ratios. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

17.
Due to its extreme mass ratio, the system AW UMa is considered as one of the most interesting contact binaries. In the present paper, a total of 1289 observations in VRI band were carried out from on 2006 March 7, 8, and 9 at Piszkesteto, Mountain Station of the Konkoly observatory (Hungary). VRI light curves were constructed and a photometric solution of these light curves was obtained by means of Willson-Devinney code. The results show that the primary component is more massive and hotter than the primary component by ～140 K. A secular period decrease with a rate dP/dE=2.436×10?10 day/cycle was detected. Based on the physical parameters of the system, we investigate the evolutionary state of the components. The primary component is above the zero age main sequence (ZAMS) track, while the secondary component has a larger radius and luminosity than expected from its ZAMS mass.  相似文献   

18.
Observations of V535 Ara obtained with IUE define the light curve of this long-period W UMa binary in the ultraviolet and let us estimate its gravity darkening. This star was chosen as a contact binary near the high-T eff limit for convection. The ultraviolet colours and spectral type correspond to (B–V)0=0.24, or A8V, and imply the star should have very little residual convection in its envelope. The gravity darkening thus ought to be large, as in a radiative star, unless it is modified by circulation in the common envelope, or unless all stars this warm are convective. The light-curve analysis is complicated by a long-term wave that depresses the orbital phases before and after secondary eclipse. We have obtained four solutions to a combination of optical and ultraviolet light curves, two for high, radiative gravity darkening and two for low, convective gravity darkening. For each value of the gravity-darkening exponent, we let the larger, more massive binary component either (a) have a dark spot in its back side or (b) have an excessively hot side facing its companion. The light curves were fitted equally well in all four cases; however, in all but the one with low-gravity darkening and a hot inner face there was a rather large global temperature difference between the two stars. The primary component of this system appears to be significantly undermassive for its spectral type, more so than the primary in AW UMa, but this probably results simply from systematic errors in a radial-velocity solution by Schöffel. It is suggested that the W UMa binaries are found only at spectral types later than about A8 because their outer envelopes must be convective to transfer luminosity.  相似文献   

19.
We present the results of a radial velocity (RV) survey of 46 subdwarf B (sdB) and 23 helium-rich subdwarf O (He-sdO) stars. We detected 18 (39%) new sdB binary systems, but only one (4%) He-sdO binary. Orbital parameters of nine sdB and sdO binaries, derived from follow-up spectroscopy, are presented. Our results are compared with evolutionary scenarios and previous observational investigations.  相似文献   

20.
We present a new multicolor CCD photometry and light curve analysis of two eclipsing binary systems, 1SWASP J133417.80 + 394314.4 and V2790 Orion. The photometric solutions for both binaries were carried out using the updated version of the Wilson– Devinney code. The results showed that first systems is A- type W UMa with mass ratios q = 0.158 while the second system is W- type with q = 3.2. The systems show over contact configuration with fill-out factors of f = 43% and 14% respectively. We calculated the orbital and absolute physical parameters for both systems and investigated their evolutionary state.  相似文献   

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