基于 LAMOST 和 APOGEE 大样本光谱巡天数据研究银河系双星的统计特征

The fraction and orbital parameters statistics of binary stars connect questions of Galactic mass models and studying the astrophysical process of stellar evolution in different populations. This fraction always is concerned at two different field: stellar physics, and Galactic structure and evolution. Understanding the fraction and orbital parameters distributions of binary stars in some environments helps us create and complete Galactic models and evolution of stellar populations, and plays the key role in the future. LAMOST is being executing its Galactic stellar spectral survey in next years. During LAMOST’s program, 10 million stellar spectra will be observed and obtained finally. Based on the changes of radial velocities (RVs) of repeat observations, this project determines the fraction of binary stars in the Milky Way with specific models and Bayesian maximum likelihood estimation method. And then stellar physical parameters derived via LAMOST’s spectra are applied to research the relationships between the fractions and stellar spectral types, and chemical abundance (stellar population). The model parameter sets will be discussed by effects of changing fraction of binary stars with our methods. This project, also, provides the accuracy of RV measurement of LAMOST regular survey, independently. Repeating quality RV data from APOGEE sample is employed to estimate parameterized distributions of orbital parameters with orbital models and Bayesian method. Based on these results and stellar age estimations, we discuss the evolutions of the fraction and parameters statistics of binary stars.

银河系双星比例和轨道参数的统计分布联系着恒星形成、银河系结构与演化两个研究领域共同关注的问题，对其深入讨论只能依赖高效率的大样本光谱巡天。理解环境中的双星所占比例和双星轨道参数特征分布对完善银河系模型和研究恒星星族演化的物理过程都有着关键作用。利用 LAMOST 开展的银河系恒星光谱巡天项目计划5年内获得千万条恒星光谱，当中包含未知比例的大量双星。产生的大样本光谱数据适于这项研究。本项目计划基于重复观测的恒星视向速度变化，使用模型构建和贝叶斯统计方法，获得银河系双星的比例，再结合光谱导出的恒星物理参数，研究双星比例与恒星光谱型、金属丰度（星族）的关系，并讨论模型参数选取对方法的影响。本项目的完成也将独立地给出 LAMOST 的视向速度测量精度。利用 APOGEE 的高精度重复视向速度观测，结合双星轨道模型，给出双星轨道特征的参数化分布，并结合对年龄的估计来讨论这些参数随时间的演化。

双星是天体物理学的重要问题，双星的比例联系着恒星演化和银河系的总体质量等关键问题，但是对双星比例的理解还停留在粗略估计的阶段。本项目利用 LAMOST 等海量恒星光谱数据，挖掘其中重复观测的光谱，结合恒星演化模型，估计出样本中的双星比例。再结合恒星物理参数，分析双星比例与恒星有效温度和金属丰度之间的相关性。这是天文学第一次确认发现银河系的双星比例随着金属丰度的增加而下降。