2dF-AAOmega spectroscopy of massive stars in the Magellanic Clouds

The north-eastern region of the Large Magellanic Cloud^⋆,⋆⋆

¹ UK Astronomy Technology Centre, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
e-mail: chris.evans@stfc.ac.uk
² Astrophysics Group, School of Physical and Geographical Sciences, Lennard-Jones Laboratories, Keele University, ST5 5BG, UK
³ Institute for Physics and Astronomy, University of Potsdam, 14476 Potsdam, Germany
⁴ Astrophysics Research Institute, Liverpool John Moores University, Liverpool Science Park ic2, 146 Brownlow Hill, Liverpool L3 5RF, UK

Received: 13 February 2015
Accepted: 5 August 2015

Abstract

We present spectral classifications from optical spectroscopy of 263 massive stars in the north-eastern region of the Large Magellanic Cloud. The observed two-degree field includes the massive 30 Doradus star-forming region, the environs of SN1987A, and a number of star-forming complexes to the south of 30 Dor. These are the first classifications for the majority (203) of the stars and include eleven double-lined spectroscopic binaries. The sample also includes the first examples of early OC-type spectra (AAΩ 30 Dor 248 and 280), distinguished by the weakness of their nitrogen spectra and by C IV λ4658 emission. We propose that these stars have relatively unprocessed CNO abundances compared to morphologically normal O-type stars, indicative of an earlier evolutionary phase. From analysis of observations obtained on two consecutive nights, we present radial-velocity estimates for 233 stars, finding one apparent single-lined binary and nine (>3σ) outliers compared to the systemic velocity; the latter objects could be runaway stars or large-amplitude binary systems and further spectroscopy is required to investigate their nature.