密近双星中额外伴星的搜寻及其稳定性研究

Recently, the observation and study on the circumbinary stellar companions, especially on the exoplanets in the close binaries, have been one of the key topics in astrophysics. Additional components may generally exist in the binaries, although this opion may further be identified observationally. Due to the accurate physical parameters of binaries, it is important for us to search the additional companions and to study their dynamical stabilities. In this project, three types of binaries will be observed by CCD photometry, in order to obtain new data. Through analyzing the light curves, the absoult parameters and evolutionary states of close binaries are determined. Based on the database of the light minimum times, the cyclic oscillation is searched from the O-C curve, which may be attributed to the light-light orbit effect via the presence of the additional body. The relation between the period of the third body and the period of the binary is then discussed. Based on the orbital parameters of the third and fourth bodies in close binaries, their stabilities of moving orbits will be investigated by the hybrid symplectic integrator. The angular momentum of the third body and its percentage of the total angular momentum of the binary system are computed. When the additional companion escapes from the central system, the orbital separation between both components will be shrinken. The new mechanism for the formation, evolution and merge of the close binary is explored. Therefore, the investigations on the additional companions will provide the new observational evidence for the possible evolutionary scenario of the close binary, which may impregnate new vigour and vitality in its evolutionary theory.

近年来，密近双星的星周伴星（特别是系外行星）的观测和研究已成为天体物理领域的热点之一。额外伴星在双星中可能普遍存在,尽管这还需要在观测上进一步证实。由于双星可以提供准确的物理参数，搜寻它们的额外伴星并研究其动力学稳定性具有重要的研究意义。本项目旨在对三种类型的密近双星进行CCD测光，以获取新的观测资料。通过光变曲线的分析，确定密近双星的绝对参数和演化状态；基于双星的光极小时刻数据库,通过O-C曲线搜寻光时轨道效应所致的周期性变化，研究双星与伴星的轨道周期之间的相关性；根据第三、四天体的轨道参数，利用辛算法研究双星系统中额外伴星运动轨道的稳定性；计算第三天体所携带的角动量及其在系统总角动量中所占的比例，研究这类伴星逃离系统而致使双星轨道收缩，探索密近双星形成、演化和并合的新机制。因此，额外伴星的研究为双星可能的演化途径提供了新的观测证据，也为双星演化的理论注入了新的生机和活力。

密近双星的星周伴星观测与搜寻，已成为天体物理领域的研究热点之一。本项目旨在对三种类型的密近双星进行CCD测光和光谱观测，以获取新的观测资料。通过求解二十颗样本星的光变曲线，确定密近双星的绝对参数和演化状态；基于食双星的光极小时刻数据库,通过O-C曲线发现十六颗样本双星存在轨道周期的周期性变化。一些主要的发现如下：（1）在五颗早型的双星系统（V548 Cyg、WW Gem、CT Tau、GU Mon和V701 Sco）存在大质量的第三天体；（2）两颗类太阳相接双星OO Aql和AK Her中发现双周期变化；（3）发现短周期的oEA型双星EU Peg可能存在第三天体：（4）另外八颗双星样本（EP Aur、AX Cas、V1107 Cas、ZZ Cyg、AR Dra、EU Hya、PS Vir和AW Vul）的轨道周期存在周期性变化。最后我们对二十六颗有周期性变化的双星样本进行统计，发现双星在演化过程中存在质量损失，考虑系统的动力学稳定性，我们排除了三颗双星存在额外伴星的可能。通过对密近双星中额外伴星的研究，为双星可能的演化途径提供了新的观测证据，也为双星演化的理论的发展和完善注入了新的生机。