短周期Algol型双星的观测与研究

In this project, the short-period Algol-type binaries (i.e., P<1.5d) will be photometrically observed in multiple bands in order to study mass transfer between components, angular momentum loss from the binary systems, and possible pulsation of component, the third body and evolutionary scenarios. Due to their wide distribution, reliable physical parameters and many complicated physical processes, Algol-type binaries have been one of the important studying topics in stellar physics. Through analyzing the light curves, we may determine accurate physical parameters, and understand their geometric features and evolutionary states. For the oEA-type variable stars, small oscillation light (i.e., the observed light curves after removed by variable light of eclipses) will be analyzed to obtain multiple frequencies and to recognize pulsation mode, which may understand the changes of stellar internal structure and physical mechanism of pulsation of component. Using the data of light minimum times, the changes of orbital periods for the sample binaries can be studied to determine the mass transfer rate of the less massive component, the angular momentum loss rate of the binary system, and the physical parameters of the possible third body. Combined the features of orbital period variations, the possible evolutionary traces from the semi-detached configuration to the contact one may be obtained. Therefore, observing the short-period Algol-type binaries may play a crucial role in understanding the internal complicated physical process of star and evolutionary link between different types of binaries.

本项目旨在对短周期Algol型双星（P<1.5天）进行多色测光，研究子星间的物质交流和系统的角动量损失、可能的子星脉动、第三天体和演化途径。由于Algol型双星的分布广泛、可靠的物理参数和各种复杂的物理过程，使得此类双星成为恒星物理领域的研究热点之一。通过光变曲线的分析，使我们能够准确地确定双星的物理参数，了解它们的几何特征和演化状态；对oEA型变星的小振幅光变（光曲线除出食光变后）进行多重频率分析和振动模式辨认，研究双星系统的内部结构变化和子星脉动的物理机制。利用光极小时刻资料，研究样本星的轨道周期变化，确定次星的质量转移率、系统的角动量损失率、可能存在的第三天体物理参数。最后，结合轨道周期变化特征，探索出短周期Algol型半分离双星演化成相接双星的可能途径。因此，通过对短周期Algol型双星的观测，为弄清双星内部的复杂物理过程和不同类型双星之间的演化联系将具有起到至关重要的作用。

Algol型双星是由一个没有充满洛希瓣的大质量的主序星和一个充满洛希瓣的小质量巨星或者亚巨星组成的半分离双星系统。短周期Algol型双星是轨道周期小于1.5天的观测样本。本项目利用国内几个小望远镜对十九颗样本星进行CCD测光，获得新的多色观测资料。通过求解十二颗食双星的光变曲线，获得了样本星的几何特征和演化状态；周期分析表明：四颗双星（DI Peg、AF Gem、AX Cas、V1241 Tau）轨道周期存在光时轨道效应，UU Leo和XZ And存在周期长期增加叠加周期性变化。这种周期性变化可能是额外伴星所致，它们可以从中心系统提取角动量是此类演化成相接双星；我们首先发现两颗新的oEA变星，半分离双星FR Ori子星的脉动可能是由于质量吸积所致，分离双星EU Peg的脉动可能由于内部结构变化。最后，我们对样本星进行统计获得了一些参量的相关性，即oEA变星脉动周期与轨道周期、具有周期性变化的EB/EW型双星系统总质量与轨道周期、短周期Algol型双星主子星的相接度与轨道周期之间的关系。通过对短周期Algol型双星的观测对研究子星间的质量转移、子星脉动、磁活动和第三天体等许多复杂的物理现象具有重要意义。