The multiplicity of massive stars in the Scorpius OB1 association through high-contrast imaging

Abstract

One of the most remarkable properties of massive stars is that almost all of them are found in binaries or higher-order multiple systems. Observations that cover the full companion mass ratio and separation regime are essential to constrain massive star and binary formation theories. We used VLT/SPHERE to characterise the multiplicity properties of 20 OB stars in the active star-forming region Sco OB1. We simultaneously observed with the IFS and IRDIS instruments, obtaining high-contrast imaging observations that cover a field of view of 1".73 x 1".73 in YJH bands and 11" x 12".5 in $K_1$ and $K_2$ bands, respectively, corresponding to a separation range between $\sim$200 and 9000 AU. The observations reach contrast magnitudes down to $\Delta K_1\sim 13$, allowing us to detect companions at the stellar-substellar boundary. In total, we detect 789 sources, most of which are likely background or foreground objects. We obtain SPHERE companion fractions of $2.3\pm 0.4$ and $4.2\pm 0.8$ for O- and B-type stars, respectively. Including all previously detected companions, we find a total multiplicity fraction of $0.89\pm 0.07$ for our sample in the range of $\sim$0-12000 AU. In conclusion, SPHERE explores an as of yet uncharted territory of companions around massive stars, which is crucial to ultimately improve our understanding of massive star and binary formation.

19 pages, 10 figures, accepted for publication in A&A

References in corpus (20)

• The Gaia mission
• Binary interaction dominates the evolution of massive stars
• Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3
• Southern Massive Stars at High Angular Resolution: Observational Campaign and Companion Detection
• The High Angular Resolution Multiplicity of Massive Stars
• Star formation through gravitational collapse and competitive accretion
• An Analysis of the Shapes of Interstellar Extinction Curves. VII. Milky Way Spectrophotometric Optical-through-Ultraviolet Extinction and Its R-Dependence
• Toward Complete Statistics of Massive Binary Stars: Penultimate Results from the Cygnus OB2 Radial Velocity Survey
• The VLT-FLAMES survey of massive stars: Evolution of surface N abundances and effective temperature scales in the Galaxy and Magellanic Clouds
• VIP: Vortex Image Processing package for high-contrast direct imaging
• Fragmentation of Massive Protostellar Disks
• An XMM-Newton view of the young open cluster NGC 6231 -- II. The OB star population
• Performance of the VLT Planet Finder SPHERE II. Data analysis and Results for IFS in laboratory
• Variability of OB stars from TESS southern Sectors 1-13 and high-resolution IACOB and OWN spectroscopy
• Investigating the lack of main-sequence companions to massive Be stars
• Adaptive Optics Photometry and Astrometry of Binary Stars. III. A Faint Companion Search of O-Star Systems
• A Chandra X-ray study of the young star cluster NGC 6231: low-mass population and initial mass function
• A Survey for High-Mass Eclipsing Binaries
• A new look at Sco OB1 association with Gaia DR2
• Probing the low-mass end of the companion mass function for O-type stars