Tracing the development of dust around evolved stars: The case of 47 Tuc

Abstract

We observed mid-infrared (7.5-22 mum) spectra of AGB stars in the globular cluster 47 Tuc with the Spitzer telescope and find significant dust features of various types. Comparison of the characteristics of the dust spectra with the location of the stars in a logP-K-diagram shows that dust mineralogy and position on the AGB are related. A 13 mum feature is seen in spectra of low luminosity AGB stars. More luminous AGB stars show a broad feature at 11.5 mum. The spectra of the most luminous stars are dominated by the amorphous silicate bending vibration centered at 9.7 mum. For 47 Tuc AGB stars, we conclude that early on the AGB dust consisting primarily of Mg-, Al- and Fe oxides is formed. With further AGB evolution amorphous silicates become the dominant species.

2 figures, accepted for publication in ApJ Letters

Cited by in corpus (16)

• The ACS Nearby Galaxy Survey Treasury IX. Constraining asymptotic giant branch evolution with old metal-poor galaxies
• The dust condensation sequence in red super-giant stars
• Optical constants of refractory oxides at high temperatures
• Giants in the globular cluster omega Centauri: dust production, mass loss and distance
• The mid-infrared colour-magnitude relation of early-type galaxies in the Coma cluster as measured by Spitzer-IRS
• Dust, pulsation, chromospheres and their role in driving mass loss from red giants in Galactic globular clusters
• A Spitzer Space Telescope Atlas of omega Centauri: The Stellar Population, Mass Loss, and the Intracluster Medium
• Modelling Long-Period Variables -- II. Fundamental mode pulsation in the nonlinear regime
• Ejection of globular cluster interstellar media through ionization by white dwarfs
• Abundance analysis for long-period variables II. RGB and AGB stars in the globular cluster 47\,Tuc
• Interplay between pulsation, mass loss, and third dredge-up: More about Miras with and without technetium
• Asteroseismology of luminous red giants with Kepler. II. Dependence of mass loss on pulsations and radiation
• Circumstellar CO in metal-poor stellar winds: the highly irradiated globular cluster star 47 Tucanae V3
• Circumstellar CO J = 3-2 detected around the evolving metal-poor ([Fe/H] ~ -1.15 dex) AGB star RU Vulpeculae
• The impact of third dredge-up on the mass loss of Mira variables
• Dust Production around Carbon-Rich Stars: The Role of Metallicity