The VLT-FLAMES Tarantula Survey

XVIII. Classifications and radial velocities of the B-type stars^⋆

¹ UK Astronomy Technology Centre, Royal Observatory, Blackford Hill, EH9 3HJ Edinburgh, UK
e-mail: chris.evans@stfc.ac.uk
² Department of Physics & Astronomy, Queen’s University Belfast, Belfast BT7 1NN, Northern Ireland, UK
³ Dept. of Physics & Astronomy, University College London, Gower Street, WC1E 6BT, London, UK
⁴ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
⁵ Institute of Astronomy with NAO, Bulgarian Academy of Sciences, PO Box 136, 4700 Smoljan, Bulgaria
⁶ Department of Physics & Astronomy, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK
⁷ Astronomical Institute Anton Pannekoek, Amsterdam University, Science Park 904, 1098 XH, Amsterdam, The Netherlands
⁸ Observatories of the Carnegie Institution for Science, 813 Santa Barbara St., Pasadena, CA 91101, USA
⁹ Cahill Center for Astrophysics, California Institute of Technology, Pasadena, CA 91125, USA
¹⁰ Institute voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, 3001, Leuven, Belgium
¹¹ Department of Physics, Faculty of Engineering & Physical Sciences, University of Surrey, Guildford, GU2 7XH, UK
¹² Instituto de Astrofísica de Andalucía-CSIC, Glorieta de la Astronomía s/n, 18008 Granada, Spain
¹³ ESA/STScI, 3700 San Martin Drive, Baltimore, MD 21218, USA
¹⁴ Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain
¹⁵ Departamento de Astrofísica, Universidad de La Laguna, 38205 La Laguna, Tenerife, Spain
¹⁶ Armagh Observatory, College Hill, Armagh, BT61 9DG, UK

Received: 17 June 2014
Accepted: 25 August 2014

Abstract

We present spectral classifications for 438 B-type stars observed as part of the VLT-FLAMES Tarantula Survey (VFTS) in the 30 Doradus region of the Large Magellanic Cloud. Radial velocities are provided for 307 apparently single stars, and for 99 targets with radial-velocity variations which are consistent with them being spectroscopic binaries. We investigate the spatial distribution of the radial velocities across the 30 Dor region, and use the results to identify candidate runaway stars. Excluding potential runaways and members of two older clusters in the survey region (SL 639 and Hodge 301), we determine a systemic velocity for 30 Dor of 271.6 ± 12.2 kms^-1 from 273 presumed single stars. Employing a 3σ criterion we identify nine candidate runaway stars (2.9% of the single stars with radial-velocity estimates). The projected rotational velocities of the candidate runaways appear to be significantly different to those of the full B-type sample, with a strong preference for either large (≥345 kms^-1) or small (≤65 kms^-1) rotational velocities. Of the candidate runaways, VFTS 358 (classified B0.5: V) has the largest differential radial velocity (−106.9 ± 16.2 kms^-1), and a preliminary atmospheric analysis finds a significantly enriched nitrogen abundance of 12 + log (N/H) ≳ 8.5. Combined with a large rotational velocity (v_esini = 345 ± 22 kms^-1), this is suggestive of past binary interaction for this star.