SAGE-Var: An Infrared Survey of Variability in the Magellanic Clouds

TL;DR

This paper reports on the SAGE-Var infrared survey of the Magellanic Clouds, revealing new variable stars and refining period-luminosity relations for Cepheids and AGB stars through multi-epoch observations at 3.6 and 4.5 microns.

Contribution

It provides the first infrared variability catalog for the Magellanic Clouds with multiple epochs, identifying new variables and improving period-luminosity relations for key stellar types.

Findings

Discovered 16 large amplitude AGB variables missed in optical surveys.

Provided infrared period-luminosity relations for Cepheids and AGB stars.

Covered variability on timescales from ~20 days to ~5 years.

Abstract

We present the first results from the SAGE-Var program, a follow on to the Spitzer legacy program Surveying the Agents of Galaxy Evolution (SAGE; Meixner, et al. 2006). We obtained 4 epochs of photometry at 3.6 & 4.5 microns covering the bar of the Large Magellanic Cloud (LMC) and the central region of the Small Magellanic Cloud (SMC) in order to probe the variability of extremely red sources missed by variability surveys conducted at shorter wavelengths, and to provide additional epochs of observation for known variables. Our 6 total epochs of observations allow us to probe infrared variability on 15 different timescales ranging from ~20 days to ~5 years. Out of a full catalog of 1,717,554 (LMC) and 457,760 (SMC) objects, we find 10 (LMC) and 6 (SMC) large amplitude AGB variables without optically measured variability owing to circumstellar dust obscuration. The catalog also contains multiple observations of known AGB variables, type I and II Cepheids, eclipsing variables, R CrB stars and young stellar objects which will be discussed in following papers. Here we present infrared Period-Luminosity (PL) relations for classical Cepheids in the Magellanic Clouds, as well as improved PL relationships for AGB stars pulsating in the fundamental mode using mean magnitudes constructed from 6 epochs of observations.