The VLT-FLAMES Tarantula Survey XXII. Multiplicity properties of the B-type stars

P. R. Dunstall, P. L. Dufton, H. Sana, C. J. Evans, I. D. Howarth, S. Simón-Díaz, S. E. De Mink, N. Langer, J. Maíz Apellániz, W. D. Taylor

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Abstract

We investigate the multiplicity properties of 408 B-type stars observed in the 30 Doradus region of the Large Magellanic Cloud with multi-epoch spectroscopy from the VLT-FLAMES Tarantula Survey (VFTS). We use a cross-correlation method to estimate relative radial velocities from the helium and metal absorption lines for each of our targets. Objects with significant radial-velocity variations (and with an amplitude larger than 16 km s<sup>-1</sup>) are classified as spectroscopic binaries. We find an observed spectroscopic binary fraction (defined by periods of <10<sup>3.5</sup> d and mass ratios >0.1) for the B-type stars, f<inf>B</inf>(obs) = 0.25 ± 0.02, which appears constant across the field of view, except for the two older clusters (Hodge 301 and SL 639). These two clusters have significantly lower binary fractions of 0.08 ± 0.08 and 0.10 ± 0.09, respectively. Using synthetic populations and a model of our observed epochs and their potential biases, we constrain the intrinsic multiplicity properties of the dwarf and giant (i.e. relatively unevolved) B-type stars in 30 Dor. We obtain a present-day binary fraction f<inf>B</inf>(true) = 0.58 ± 0.11, with a flat period distribution. Within the uncertainties, the multiplicity properties of the B-type stars agree with those for the O stars in 30 Dor from the VFTS.

Original languageEnglish
Article numberA93
Pages (from-to)1-10
Number of pages10
JournalAstronomy and Astrophysics
Volume580
DOIs
Publication statusPublished - 01 Aug 2015

Keywords

  • Binaries: spectroscopic
  • Open clusters and associations: individual: 30 Doradus
  • Stars: early-type

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Dunstall, P. R., Dufton, P. L., Sana, H., Evans, C. J., Howarth, I. D., Simón-Díaz, S., De Mink, S. E., Langer, N., Maíz Apellániz, J., & Taylor, W. D. (2015). The VLT-FLAMES Tarantula Survey XXII. Multiplicity properties of the B-type stars. Astronomy and Astrophysics, 580, 1-10. [A93]. https://doi.org/10.1051/0004-6361/201526192