Oral Presentation Astronomical Society of Australia Annual Scientific Meeting including HWWS 2013

The Membership and Multiplicity of Sco-Cen (#51)

Aaron C Rizzuto 1 , Michael J Ireland 1
  1. Macquarie University, North Ryde, NSW, Australia

OB associations provide a glimpse into a group of stars directly after formation. The nearest OB association to the sun is the Sco-Cen association, and is also the nearest region of massive star formation. Sco-Cen provides a rich laboratory for the study of the output of star formation. Despite the relatively complete high-mass membership, the G to M-type PMS membership is highly incomplete. We have developed a Bayesian membership selection that assigns a membership probability based on position, proper motion, and photometry from all sky catalogues. Potential members will then be confirmed through spectroscopic youth indicators such as Li6708 and H-alpha using the WiFeS instrument on the 2.3m telescope. This will allow us to simultaneously search for massive planetary companions, such as GSC 06214-00210b analogs using spectroastrometric techniques. We have also characterised the multiplicity of the high-mass Sco-Cen stars using long baseline interferometry and all-sky data. We observed a 58 stars in the Sco-Cen region of sky, which were bluer that B-V = -0.1 and brighter than 5thmagnitude using the Sydney University Stellar Interferometer. We detected 24 companions, 15 of which were new detections. We then used all-sky data such as 2MASS and APASS magnitudes and UCAC4 proper motions to identify companions beyond 5 arcseconds separation. Combining our interferometric and all-sky surveys with the highly complete imaging and spectroscopic work in the literature, we used a Bayesian technique to derive the parameters of the Sco-Cen B-type multiplicity distribution. We find a companion frequency of 1.25, and estimate that as many as 23% of Sco-Cen B-type stars are single. This raises questions as to the angular momentum removal methods involved in the formation of high-mass stars. We also present preliminary results dating different parts of Sco-Cen with precision orbit measurements using long baseline interferometry and AO observations.