2dF-AAOmega spectroscopy of massive stars in the Magellanic Clouds: The north-eastern region of the Large Magellanic Cloud

TL;DR

This study provides the first spectral classifications for most massive stars in the north-eastern Large Magellanic Cloud, including new early OC-type stars, and analyzes their radial velocities to identify potential binary systems or runaways.

Contribution

It offers the first classifications for 203 stars in this region, identifies new early OC-type spectra, and presents radial velocity data to find binary candidates and runaways.

Findings

First classifications for 203 stars in the region.

Discovery of early OC-type spectra with unprocessed CNO abundances.

Identification of potential binary systems and runaway stars.

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 (AAOmega 30 Dor 248 and 280), distinguished by the weakness of their nitrogen spectra and by C IV 4658 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 (>3sigma) 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.