Spitzer/IRAC Observations of AGB stars

TL;DR

This study uses Spitzer IRAC observations to analyze the infrared properties of 48 galactic AGB stars, revealing correlations between IRAC colors, variability types, and dust features in their winds.

Contribution

First IRAC-based photometric survey of galactic AGB stars, linking infrared colors to molecular and dust features, and variability classifications.

Findings

IRAC colors are sensitive to molecular and dust features.

Period-color relation is tight for semiregular variables.

Mira variables show higher infrared excess.

Abstract

We present here the first observation of galactic AGB stars with the InfraRed Array Camera (IRAC) onboard the Spitzer Space Telescope. Our sample consists of 48 AGB stars of different chemical signature, mass loss rate and variability class. For each star we have measured IRAC photometry and colors. Preliminary results shows that IRAC colors are sensitive to spectroscopic features associated to molecules and dust in the AGB wind. Period is only loosely correlated to the brightness of the stars in the IRAC bands. We do find, however, a tight period-color relation for sources classified as semiregular variables. This may be interpreted as the lack of warm dust in the wind of the sources in this class, as opposed to Mira variables that show higher infrared excess in all IRAC bands.