RUSTY OLD STARS: A SOURCE OF THE MISSING INTERSTELLAR IRON?

Journal Article · Sat Jul 10 04:00:00 EDT 2010 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/717/2/L92· OSTI ID:21451048

McDonald, I; Zijlstra, A A; Markwick, A J ^[1]; Sloan, G C; Bernard-Salas, J ^[2]; Matsunaga, N ^[3]; Matsuura, M ^[4]

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1. Jodrell Bank Centre for Astrophysics, Alan Turing Building, Manchester, M13 9PL (United Kingdom)
2. Cornell University, Astronomy Department, Ithaca, NY 14853-6801 (United States)
3. Institute of Astronomy, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan)
4. UCL-Institute of Origins, Astrophysics Group, Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom)

Iron, the universe's most abundant refractory element, is highly depleted in both circumstellar and interstellar environments, meaning it exists in solid form. The nature of this solid is unknown. In this Letter, we provide evidence that metallic iron grains are present around oxygen-rich asymptotic giant branch stars, where it is observationally manifest as a featureless mid-infrared excess. This identification is made using Spitzer Space Telescope observations of evolved globular cluster stars, where iron dust production appears ubiquitous and in some cases can be modeled as the only observed dust product. In this context, FeO is examined as the likely carrier for the 20 {mu}m feature observed in some of these stars. Metallic iron appears to be an important part of the dust condensation sequence at low metallicity, and subsequently plays an influential role in the interstellar medium. We explore the stellar metallicities and luminosities at which iron formation is observed, and how the presence of iron affects the outflow and its chemistry. The conditions under which iron can provide sufficient opacity to drive a wind remain unclear.

• OSTI ID: 21451048
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 2 Vol. 717; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CHALCOGENIDES
DUSTS
ELEMENTS
IRON
IRON COMPOUNDS
IRON OXIDES
LUMINOSITY
METALS
NONMETALS
OPTICAL PROPERTIES
OXIDES
OXYGEN
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
STAR CLUSTERS
STARS
TELESCOPES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
UNIVERSE