Discovery of Stars Surrounded by Iron Dust in the Large Magellanic Cloud

Marini, E.; Dell’Agli, F.; Di Criscienzo, Marcella; Puccetti, Simonetta; García-Hernández, D. A.; Mattsson, Lars; Ventura, Paolo
Bibliographical reference

The Astrophysical Journal Letters, Volume 871, Issue 1, article id. L16, 5 pp. (2019).

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2019
Number of authors
7
IAC number of authors
2
Citations
10
Refereed citations
9
Description
We consider a small sample of oxygen-rich, asymptotic giant branch stars in the Large Magellanic Cloud, observed by the Spitzer Space Telescope, exhibiting a peculiar spectral energy distribution, which can hardly be explained by the common assumption that dust around Asymptotic Giant Branch stars is primarily composed of silicate grains. We suggest that this uncommon class of objects is the progeny of a metal-poor generation of stars, with metallicity Z ∼ 1–2 × 10‑3, formed ∼100 Myr ago. The main dust component in the circumstellar envelope is solid iron. In these stars the poor formation of silicates is set by the strong nucleosynthesis experienced at the base of the envelope, which provokes a scarcity of magnesium atoms and water molecules, required for the silicate formation. The importance of the present results to interpret the data from the incoming James Webb Space Telescope is also discussed.
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Nucleosynthesis and molecular processes in the late stages of Stellar Evolution
Low- to intermediate-mass (M < 8 solar masses, Ms) stars represent the majority of stars in the Cosmos. They finish their lives on the Asymptotic Giant Branch (AGB) - just before they form planetary nebulae (PNe) - where they experience complex nucleosynthetic and molecular processes. AGB stars are important contributors to the enrichment of the
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