Variability of Luminous Stars in the Large Magellanic Cloud Using 10 Years of ASAS Data

TL;DR

This study analyzes 10 years of optical data from ASAS to investigate variability in 1268 luminous stars in the Large Magellanic Cloud, discovering new variable stars and eclipsing binaries, especially among red supergiants and massive OB stars.

Contribution

It provides the first systematic variability analysis of a large sample of luminous LMC stars using decade-long ASAS data, identifying new variables and eclipsing binaries.

Findings

117 variable stars identified, 38 new discoveries.

8 new bright, massive eclipsing binaries of OB type.

Majority of variables are red supergiants, with some B and O stars.

Abstract

Motivated by the detection of a recent outburst of the massive luminous blue variable LMC-R71, which reached an absolute magnitude M_V = -9.3 mag, we undertook a systematic study of the optical variability of 1268 massive stars in the Large Magellanic Cloud, using a recent catalog by Bonanos et al. (2009) as the input. The ASAS All Star Catalog (Pojmanski 2002) provided well-sampled light curves of these bright stars spanning 10 years. Combining the two catalogs resulted in 599 matches, on which we performed a variability search. We identified 117 variable stars, 38 of which were not known before, despite their brightness and large amplitude of variation. We found 13 periodic stars that we classify as eclipsing binary (EB) stars, eight of which are newly discovered bright, massive eclipsing binaries composed of OB type stars. The remaining 104 variables are either semi- or non-periodic, the majority (85) being red supergiants. Most (26) of the newly discovered variables in this category are also red supergiants with only three B and four O stars.