Binary fraction of O and B-type stars from LAMOST data

TL;DR

This study estimates the intrinsic binary fraction of O and B-type stars using LAMOST data, employing a cross-correlation method and simulations to assess reliability, finding a binary fraction around 37-40%.

Contribution

It introduces a new approach to estimate the binary fraction of OB stars from large spectroscopic surveys, with detailed simulations to validate the method.

Findings

Binary fraction of OB stars is approximately 37-40%.

The method is reliable for stars with multiple observations.

Uncertainty increases with fewer observational epochs.

Abstract

Binary stars plays important role in the evolution of stellar populations . The intrinsic binary fraction ($f_{bin}$) of O and B-type (OB) stars in LAMOST DR5 was investigated in this work. We employed a cross-correlation approach to estimate relative radial velocities for each of the stellar spectra. The algorithm described by \cite{2013A&A...550A.107S} was implemented and several simulations were made to assess the performance of the approach. Binary fraction of the OB stars are estimated through comparing the uni-distribution between observations and simulations with the Kolmogorov-Smirnov tests. Simulations show that it is reliable for stars most of whom have $6,7$ and $8$ repeated observations. The uncertainty of orbital parameters of binarity become larger when observational frequencies decrease. By adopting the fixed power exponents of $\pi=-0.45$ and $\kappa=-1$ for period and mass ratio distributions, respectively, we obtain that $f_{bin}=0.4_{-0.06}^{+0.05}$ for the samples with more than 3 observations. When we consider the full samples with at least 2 observations, the binary fraction turns out to be $0.37_{-0.03}^{+0.03}$. These two results are consistent with each other in $1\sigma$.