Variable Evolved Stars and YSOs Discovered in the Large Magellanic Cloud using the SAGE Survey

TL;DR

This study identifies and catalogs approximately 2,000 infrared variable sources in the Large Magellanic Cloud, primarily AGB stars, using two-epoch Spitzer data from the SAGE survey, revealing variability patterns among different stellar types.

Contribution

First large-scale infrared variability survey of the LMC using Spitzer data, providing a catalog of variable sources including AGB stars and YSO candidates.

Findings

Most variable sources are AGB stars.

Over 66% of extreme AGB stars are variable.

Detected variable YSO candidates.

Abstract

We present initial results and source lists of variable sources in the Large Magellanic Cloud (LMC) for which we detect thermal infrared variability from the SAGE (Surveying the Agents of a Galaxy's Evolution) survey, which had 2 epochs of photometry separated by three months. The SAGE survey mapped a 7 degree by 7 degree region of the LMC using the IRAC and the MIPS instruments on board Spitzer. Variable sources are identified using a combination of the IRAC 3.6, 4.5, 5.8, 8.0 \micron bands and the MIPS 24 \micron bands. An error-weighted flux difference between the two epochs is used to assess the variability. Of the ~ 3 million sources detected at both epochs we find ~ 2,000 variable sources for which we provide electronic catalogs. Most of the variable sources can be classified as asymptotic giant branch (AGB) stars. A large fraction (> 66%) of the extreme AGB stars are variable and only smaller fractions of carbon-rich (6.1%) and oxygen-rich (2.0%) stars are detected as variable. We also detect a population of variable young stellar object candidates.