Variable Evolved Stars and Young Stellar Objects Discovered in the Large Magellanic Cloud Using the SAGE Survey

Vijh, Uma P., Meixner, M., Babler, B., Block, M., Bracker, S., Engelbracht, C. W., For, B., Gordon, K., Hora, J., Indebetouw, R., Leitherer, C., Meade, M., Misselt, K., Sewilo, M., Srinivasan, S., & Whitney, B.
2009, The Astronomical Journal, 137, 3139

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 Surveying the Agents of a Galaxy's Evolution (SAGE) survey, which had two epochs of photometry separated by 3 months. The SAGE survey mapped a 7° × 7° region of the LMC using the Infrared Array Camera (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 μ bands and the MIPS 24 μ 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 ~2000 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 sources. We also detect a population of variable young stellar object candidates.


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