On the possibility that the most massive stars result from binary mergers

¹ Astronomical Institute Anton Pannekoek, University of Amsterdam, Science Park 904, PO Box 94249, 1090 GE Amsterdam, The Netherlands
² Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
³ Armagh Observatory, College Hill, Armagh BT61 9DG, UK
⁴ Observatories of the Carnagie Institution for Science, 813 Santa Barbara St, Pasadena, CA 91101, USA
⁵ Cahill Center for Astrophysics, California Institute of Technology, Pasadena, CA 91125, USA
⁶ UK Astronomy Technology Centre, Royal Observatory Edinburgh, Blackford Hill, Edinburugh EH9 3HJ, UK
⁷ Argelander-Institut für Astronomie der Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
⁸ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
⁹ Instituto de Astrofísica de Canarias, C/ vía Láctea s/n, 38200 La Laguna, Tenerife, Spain
¹⁰ Departamento de Astrofísica, Universidad de La Laguna, Avda. Astrofísico Francisco Sánchez s/n, 38071 La Laguna, Tenerife, Spain

Abstract

The VLT-FLAMES Tarantula Survey is an ESO Large Program from which we have obtained multi-epoch optical spectroscopy of over 800 massive stars in the 30 Doradus region of the Large Magellanic Cloud. This unprecedented dataset is being used to address outstanding questions in how massive stars evolve from the early main sequence to their deaths as core collapse supernovae. Here we focus on the rotation properties of the population of presumably single O stars and use binary population synthesis predictions to show that the rapid rotators among this population likely are post-interaction binaries. The same type of population synthesis can be used to study the mass function of massive young clusters. We argue – on the basis of predictions for the Arches and Quintuplet clusters – that a sizable fraction of the very massive WNh stars in 30 Doradus may also have such a binary interaction history. We single out the WNh star discovered in the VFTS, VFTS 682, and discuss its properties.