# Spitzer Observations of Large Amplitude Variables in the LMC and IC 1613

## TL;DR

This paper analyzes Spitzer infrared observations of large amplitude variable stars in the LMC and IC 1613, revealing clear period-luminosity-colour relations and effects of circumstellar dust on brightness.

## Contribution

It provides new insights into the infrared properties and period-luminosity relations of AGB variables in these galaxies, especially regarding dust effects.

## Key findings

- C-rich Mira variables show a strong period-luminosity-colour relation.
- Dusty stars are approximately one magnitude brighter at 4.5 microns than dust-free stars with similar periods.
- The [4.5] period-luminosity relation is affected by circumstellar dust presence.

## Abstract

The 3.6 and 4.5 micron characteristics of AGB variables in the LMC and IC1613 are discussed. For C-rich Mira variables there is a very clear period-luminosity-colour relation, where the [3.6]-[4.5] colour is associated with the amount of circumstellar material and correlated with the pulsation amplitude. The [4.5] period-luminosity relation for dusty stars is approximately one mag brighter than for their naked counterparts with comparable periods.