# Do evolved stars in the LMC show dual dust chemistry?

## TL;DR

This study investigates evolved stars in the LMC, revealing a dual dust chemistry with carbonaceous and silicate dust, linked to their evolutionary stage and stellar mass, based on spectral analysis and stellar modeling.

## Contribution

It proposes the novel idea of dual dust chemistry in evolved LMC stars, connecting dust features to stellar evolution and formation history.

## Key findings

- Presence of dual dust chemistry with carbonaceous and silicate dust.
- Stars are low-mass, 1-4 Gyr old, in post-AGB or after-pulse phases.
- Spectral features support the dual dust chemistry hypothesis.

## Abstract

We study a group of evolved M-stars in the Large Magellanic Cloud, characterized by a peculiar spectral energy distribution. While the $9.7~\mu$m feature arises from silicate particles, the whole infrared data seem to suggest the presence of an additional featureless dust species. We propose that the circumstellar envelopes of these sources are characterized by a dual dust chemistry, with an internal region, harbouring carbonaceous particles, and an external zone, populated by silicate, iron and alumina dust grains. Based on the comparison with results from stellar modelling that describe the dust formation process, we deduce that these stars descend from low-mass ($M < 2~M_{\odot}$) objects, formed $1-4$ Gyr ago, currently evolving either in the post-AGB phase or through an after-pulse phase, when the shell CNO nuclear activity is temporarily extinguished. Possible observations able to confirm or disregard the present hypothesis are discussed.