Evolved stars in the Local Group galaxies - III. AGB and RSG stars in Sextans A

TL;DR

This study characterizes evolved stars in Sextans A, a low-metallicity galaxy, analyzing dust production and stellar evolution to understand dust enrichment in metal-poor environments.

Contribution

It provides a detailed analysis of AGB and RSG stars in Sextans A, including dust formation and production rates, using infrared data in a low-metallicity context.

Findings

Dust production rate estimated at 6×10⁻⁷ M☉/yr

Carbon stars dominate dust contribution

Identification of hot bottom burning and RSG stars

Abstract

We study the evolved stellar population of the galaxy Sextans A. This galaxy is one of the lowest metallicity dwarfs in which variable asymptotic giant branch stars have been detected, suggesting that little metal enrichment took place during the past history. The analysis consists in the characterization of a sample of evolved stars, based on evolutionary tracks of asymptotic giant branch and red super giant stars, which include the description of dust formation in their winds. Use of mid-infrared and near-infrared data allowed us to identify carbon-rich sources, stars undergoing hot bottom burning and red super giants. The dust production rate, estimated as $6\times 10^{-7} M_{\odot}/$yr, is dominated by $\sim 10$ carbon stars, with a small contribution of higher mass M-stars, of the order of $4\times 10^{-8} M_{\odot}/$yr. The importance of this study to understand how dust production works in metal-poor environments is also evaluated.