Long-baseline interferometric multiplicity survey of the Sco-Cen OB association

Abstract

We present the first multiplicity-dedicated long-baseline optical interferometric survey of the Scorpius-Centaurus-Lupus-Crux association. We used the Sydney University Stellar Interferometer to undertake a survey for new companions to 58 Sco-Cen B-type stars and have detected 24 companions at separations ranging from 7 to 130 mas, 14 of which are new detections. Furthermore, we use a Bayesian analysis and all available information in the literature to determine the multiplicity distribution of the 58 stars in our sample, showingthat the companion frequency is f = 1.35 ± 0.25 and the mass ratio distribution is best described by qγ with γ = -0.46, agreeing with previous Sco-Cen high-mass work and differing significantly from lower mass stars in Tau-Aur. Based on our analysis, we estimate that among young B-type stars in moving groups, up to 23 per cent are apparently single stars.This has strong implications for the understanding of high-mass star formation, which requires angular momentum dispersal through some mechanism such as formation ofmultiple systems.