基于LAMOST红巨星和红团簇星数据的双星比例性质研究

Binary Fractions Based on the LAMOST RGB and RC Data

基于郭守敬望远镜反银心方向巡天第二版增值星表中的56 731颗红巨星和16 582颗红团簇星样本,利用重复观测源最大视向速度差△RVmax的分布,测量了该样本的双星比例及其随演化阶段、金属丰度的变化。△RVmax的最大值与红巨星对应的表面重力加速度存在很强的正相关;演化阶段越晚,双星比例越低;金属丰度越高,双星比例越低;红巨星前身星的双星比例为(38±2)%,红团簇星前身星的双星比例为(35±3)%。该结果证实了前人基于阿帕奇点天文台银河系演化实验DR13巨星样本的结果。此外,我们还发现了46个可能包含大质量致密星的双星候选体,值得进一步的研究。

Binary stars are ubiquitous in the universe. Measuring binary fractions and their variations in different stellar populations has important implications in the studies of a number of research fields including star formation and evolution, gravitational wave detections, galactic structure and stellar population synthesis. Taking advantage of large scale surveys, statistical methods have been developed to measure binary fractions in the Galaxy, but the existing studies are mainly for main-sequence stars. Red giant stars and red clump stars in the late stages of stellar evolution, are ideal tracers to probe properties and evolution of binary stars. However, measurements of binary fractions for giant stars are very rarely reported. In this work, based on a large sample of red giant stars and red clumps from the 2 nd value-added catalog of LAMOST Spectroscopic Survey of the Galactic Anti-center, we investigate the binary fractions and their variations with stellar evolution stages and metallicities, using the method of distribution of △RVmax. We find that there is a strong correlation between △RVmaxand their evolution stage. The later stages the evolution is in, the lower value the binary fraction has. And the binary fraction decreases as metallicity increases. Our simulation shows that binary fraction of giant stars during their main-sequence stage is about(38±2)%, slightly higher but consistent with the result of Badenes et al.(2018) based on the APOGEE DR13. A number of 46 candidates of compact binary systems are also reported.