Do evolved stars in the LMC show dual dust chemistry?

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 ($M<2M_{\odot }$) 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.

References in corpus (26)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• Spitzer Survey of the Large Magellanic Cloud, Surveying the Agents of a Galaxy's Evolution (SAGE) I: Overview and Initial Results
• The Star Formation History of the Large Magellanic Cloud
• The Magellanic Clouds Photometric Survey: The Large Magellanic Cloud Stellar Catalog and Extinction Map
• Post-Asymptotic Giant Branch Evolution of Low- and Intermediate-Mass Stars. Preliminary Results
• New models for the evolution of Post-Asymptotic Giant Branch stars and Central Stars of Planetary Nebulae
• The SAGE-Spec Spitzer Legacy program: The life-cycle of dust and gas in the Large Magellanic Cloud. Point source classification I
• The dust production rate of AGB stars in the Magellanic Clouds
• Dust from AGBs: relevant factors and modelling uncertainties
• Spitzer Infrared Spectrograph Observations of Magellanic Cloud Planetary Nebulae: the nature of dust in low metallicity circumstellar ejecta
• The Mass-Loss Return From Evolved Stars to the LMC: Empirical Relations for Excess Emission at 8 and 24 μm
• The SAGE-Spec Spitzer Legacy program: The life-cycle of dust and gas in the Large Magellanic Cloud
• Unusual Dust Emission from Planetary Nebulae in the Magellanic Clouds
• Luminosities and mass-loss rates of Local Group AGB stars and Red Supergiants
• AGB stars in the LMC: evolution of dust in circumstellar envelopes
• The mixed chemistry phenomenon in Galactic Bulge PNe
• Carbon chemistry in Galactic Bulge Planetary Nebulae
• The trigger of the AGB superwind: the importance of carbon
• AGB stars in the SMC: evolution and dust properties based on Spitzer observations
• Chemical Abundances and Dust in Planetary Nebulae in the Galactic Bulge
• Spitzer detection of PAH and silicate features in post-AGB stars and young Planetary Nebulae
• Modelling the alumina abundance of oxygen-rich evolved stars in the Large Magellanic Cloud
• On the alumina dust production in the winds of O-rich Asymptotic Giant Branch stars
• Chemical abundances in Galactic planetary nebulae with Spitzer spectra
• Probing the dusty stellar populations of the Local Volume Galaxies with JWST/MIRI
• Discovery of stars surrounded by iron dust in the LMC

Cited by in corpus (3)

• Characterization of M-stars in the LMC in the JWST era
• Ashes of FIRE: Modeling Dust Grain Size Evolution in the Local Group with FIRE
• Dust Production around Carbon-Rich Stars: The Role of Metallicity