Volume 580, August 2015
|Number of page(s)||10|
|Section||Stellar structure and evolution|
|Published online||07 August 2015|
The VLT-FLAMES Tarantula Survey
1 Astrophysics Research Centre, School of Mathematics
& Physics, Queen’s University Belfast, BT7 1NN, UK
2 ESA/Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
3 UK Astronomy Technology Centre, Royal Observatory Edinburgh, Blackford Hill, Edinburgh, EH9 3HJ, UK
4 Dept. of Physics & Astronomy, University College London, Gower Street, London, WC1E 6BT, UK
5 Instituto de Astrofísica de Canarias, 38205, La Laguna, Tenerife, Spain
6 Departamento de Astrofísica, Universidad de La Laguna, 38205, La Laguna, Tenerife, Spain
7 Astronomical Institute Anton Pannekoek, Amsterdam University, Science Park 904, 1098 XH, Amsterdam, The Netherlands
8 Argelander-Institut für Astronomie der Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
9 Departamento de Astrofísica, Centro de Astrobiología (INTA-CSIC), Campus ESA, Apartado Postal 78, 28 691 Villanueva de la Cañada, Madrid, Spain
Received: 26 March 2015
Accepted: 21 May 2015
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-1) are classified as spectroscopic binaries. We find an observed spectroscopic binary fraction (defined by periods of <103.5 d and mass ratios >0.1) for the B-type stars, fB(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 fB(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.
Key words: stars: early-type / binaries: spectroscopic / open clusters and associations: individual: 30 Doradus
Appendices A, B are available in electronic form at http://www.aanda.org
Full Tables 2 and 3 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (22.214.171.124) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/580/A93
© ESO, 2015
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