The binarity of Galactic dwarf stars along with effective temperature and metallicity

The fraction of binary stars f(b) is one of most valuable tools to probe the star formation and evolution of multiple systems in the Galaxy. We focus on the relationship between f(b) and stellar metallicity [Fe/H] by employing the differential radial velocity (DRV) method and the large sample observed by the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST). Main-sequence stars from A-to K-type in the third data release of LAMOST are selected to estimate f(b). Contributions to a profile of DRV from the radial velocity (RV) error of single stars sigma(RV) and the orbital motion of binary stars are evaluated from the DRV profile. We employ 365 911 stars with randomly repeating spectral observations to present a detailed analysis of f(b) and sigma(RV) in the two-dimensional space of T-eff and [Fe/H]. The A-type stars are more likely to be companions in binary star systems than other stars. Furthermore, the reverse correlation between f(b) and [Fe/H] can be shown statistically, which suggests that f(b) is a joint function of T-eff and [Fe/H]. At the same time, sigma(RV) of the sample are fitted for different T-eff and [Fe/H]. Metal-rich cold stars in our sample have the best RV measurement.