LAMOST DR8 early-type stars statistical properties

We collect 886 early-type stars, each with more than six observations from the LAMOST DR8, and divide the sample into subgroups based on their derived effective temperature (Teff), metallicity ([M/H]), and projected rotational velocity (vsini). Radial velocity measurements were archived from a prior study. A set of Monte-Carlo simulations, following distributions of f(P) {prop.to} P^{pi}^and f(q) {prop.to} q^{gamma}^ were applied to the observed binary fraction to correct for any observational biases.

The uncertainties of the derived results induced by the sample size and observation frequency are examined systematically. We found that f^in^_b_ increases with increasing Teff. For stars in groups of B8-A, B4-B7, O-B3, the binary fractions are f^in^_b_=48%+/-10%, 60%+/-10%, and 76%+/-10%, respectively.

The binary fraction is positively correlated with metallicity for spectra in the sample, with derived values of f^in^_b_=44%+/-10%, 60%+/-10% and 72%+/-10% for spectra with metallicity spanning from [M/H]<-0.55, -0.55<=[M/H]<-0.1, to [M/H]>=-0.1. Over all the vsini values we have considered, the f^in^_b_ have constant values as ~50%. It seems that the binary population is relatively evenly distributed over a wide range of vsini values, while the whole sample shows that most of the stars are concentrated in low values of vsini (probably from strong wind and magnetic braking of single massive stars), and in high values of vsini (likely from the merge of binary stars) in cases.

Stellar evolution and binary interaction may be partly responsible for this. In case of observations with more than six observations, we have derived {pi}=-0.9+/-0.35, -0.9+/-0.35, and -0.9+/-0.35, and {gamma}=-1.9+/-0.9, -1.1+/-0.9 and -2+/-0.9 for O-B3, B4-B7, B8-A type stars, respectively. There are no correlations being found between {pi}({gamma}) and Teff, and neither for {pi}({gamma}) and [M/H].

The uncertainties of the distribution decrease towards a larger sample size with higher observational cadence.