New progress has been made in the study of the statistical properties of LAMOST early star binaries

Recently, the international astronomical journal Astronomy & Astrophysics published online the research work of Dr. Guo Yanjun and collaborators of the Yunnan Astronomical Observatory of the Chinese Academy of Sciences on the statistical properties of early star binaries. This work uses LAMOST DR8 medium-resolution data to study the binary ratio, mass ratio distribution and periodic distribution of 886 early type stars with more than 6 observations, and gives the relationship between the proportion of early star binary stars and effective temperature, metal abundance and projected rotation speed, which provides a statistical reference for studying the formation and evolution of early type stars.

Early stars are mainly composed of stars of spectral type O and B. They are massive and luminosity. Massive early-type stars can promote cosmic reionization and enrich galaxy chemistry. Most of the early stars belong to binary star systems, and binary star systems composed of early stars may eventually evolve into gravitational wave sources such as binary neutron stars, black hole-neutron stars, and double black holes. The statistical properties of massive binary stars are crucial for tracking the formation of massive stars and limiting the properties of binary populations, and have been a key research topic in astronomy. At present, most of the observation samples of early stars come from different observations, and the lack of consistent observation samples leads to a large bias in the results of the statistical properties of early star binaries.

The study used 886 samples of early type stars in LAMOST DR8 with more than 6 spectral observations, grouped according to their effective temperature, metal abundance and projection rotation velocity, and comprehensively corrected the observation data in combination with Monte Carlo simulation. It is found that the proportion of intriguing binaries in this batch of early type stars decreases with decreasing temperature, and decreases with the decrease of metal abundance: the proportion of binary stars of massive O/B type stars can reach 76%, while the proportion of binary stars of relatively small mass B/A type stars is about 48%; Metallic-like abundance-like solar ([M/H]>-0.1) has a 72% proportion of early-type binary stars, while the metal abundance is poorer ([M/H]<-0.5) has a 44% proportion of early-type binary stars (see Figure 1). This result can be used as an input parameter for binary population synthesis to understand the formation and evolution of compact binary stars.

Figure 1: Intrinsic binary ratio vs. spectral type and metal abundance

The research results have been funded by the National Natural Science Foundation of China and other projects. (Source: Yunnan Astronomical Observatory, Chinese Academy of Sciences)

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