Letter to the Editor

The VLT-FLAMES Tarantula Survey

II. R139 revealed as a massive binary system

¹ Institute for Astronomy, Royal Observatory Edinburgh, Blackford Hill, Edinburgh. EH9 3HJ, UK
e-mail: wdt@roe.ac.uk
² UK Astronomy Technology Centre, Royal Observatory Edinburgh, Blackford Hill, Edinburgh. EH9 3HJ, UK
³ Astronomical Institute Anton Pannekoek, University of Amsterdam, Science Park 904, 1098XH Amsterdam, The Netherlands
⁴ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
⁵ Department of Physics and Astronomy, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK
⁶ Faulkes Telescope Project, University of Glamorgan, Pontypridd, CF37 1DL, Wales, UK
⁷ European Southern Observatory, Alonso de Cordova 3107, Casilla 19001, Santiago 19, Chile
⁸ Departamento de Física, Universidad de La Serena, Cisternas 1200 Norte, La Serena, Chile
⁹ Instituto de Ciencias Astronomicas, de la Tierra, y del Espacio(ICATE-CONICET), Av. Espana 1512 Sur, 5400 San Juan, Argentina
¹⁰ Armagh Observatory, College Hill, Armagh, BT61 9DG, Northern Ireland, UK
¹¹ Institute of Astronomy & Astrophysics, National Observatory of Athens, I. Metaxa & Vas. Pavlou Street, P. Penteli 15236, Greece
¹² Astronomical Institute, Utrecht University, Princetonplein 5, 3584 CC, Utrecht, The Netherlands
¹³ University of Vienna, Department of Astronomy, Türkenschanzstr. 17, 1180 Vienna, Austria
¹⁴ Dept. of Physics & Astronomy, Hounsfield Road, University of Sheffield, S3 7RH, UK
¹⁵ Argelander-Unstitut fur Astronomie der Universitat Bonn, Auf dem Hugel 71, 53121 Bonn, Germany
¹⁶ Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain
¹⁷ Departamento de Astrofísica, Universidad de La Laguna, Astrofísico Francisco Sánchez, 38071 La Laguna, Tenerife, Spain
¹⁸ Instituto de Astrofísica de Andalucía-CSIC, Glorieta de la Astronomía s/n, 18008 Granada, Spain
¹⁹ Institute of Astronomy with National Astronomical Observatory, Bulgarian Academy of Sciences, PO Box 136, Smoljan, Bulgaria
²⁰ Las Campanas Observatory, Carnegie Observatories, Casilla 601, La Serena, Chile

Received: 25 February 2011
Accepted: 28 March 2011

Abstract

We report the discovery that R139 in 30 Doradus is a massive spectroscopic binary system. Multi-epoch optical spectroscopy of R139 was obtained as part of the VLT-FLAMES Tarantula Survey, revealing a double-lined system. The two components are of similar spectral types; the primary exhibits strong C III λ4650 emission and is classified as an O6.5 Iafc supergiant, while the secondary is an O6 Iaf supergiant. The radial-velocity variations indicate a highly eccentric orbit with a period of 153.9 days. Photometry obtained with the Faulkes Telescope South shows no evidence for significant variability within an 18 month period. The orbital solution yields lower mass limits for the components of M₁sin³i = 78  ±  8   M_⊙ and M₂sin³i = 66  ±  7   M_⊙. As R139 appears to be the most massive binary system known to contain two evolved Of supergiants, it will provide an excellent test for atmospheric and evolutionary models.