ALMA reveals sunburn: CO dissociation around AGB stars in the globular cluster 47 Tucanae

Abstract

ALMA observations show a non-detection of carbon monoxide around the four most luminous asymptotic giant branch (AGB) stars in the globular cluster 47 Tucanae. Stellar evolution models and star counts show that the mass-loss rates from these stars should be ~1.2-3.5 x 10^-7 solar masses per year. We would naively expect such stars to be detectable at this distance (4.5 kpc). By modelling the ultraviolet radiation field from post-AGB stars and white dwarfs in 47 Tuc, we conclude CO should be dissociated abnormally close to the stars. We estimate that the CO envelopes will be truncated at a few hundred stellar radii from their host stars and that the line intensities are about two orders of magnitude below our current detection limits. The truncation of CO envelopes should be important for AGB stars in dense clusters. Observing the CO (3-2) and higher transitions and targeting stars far from the centres of clusters should result in the detections needed to measure the outflow velocities from these stars.

14 pages, 4 figures, accepted MNRAS

References in corpus (22)

• Modules for Experiments in Stellar Astrophysics (MESA)
• The ACS Nearby Galaxy Survey Treasury IX. Constraining asymptotic giant branch evolution with old metal-poor galaxies
• On the nature of star-forming filaments: I. Filament morphologies
• Dynamics of Planetary Systems in Star Clusters
• Mass loss on the red giant branch: the value and metallicity dependence of Reimers' η in globular clusters
• The First Empirical Mass Loss Law for Population II Giants
• Giants in the globular cluster omega Centauri: dust production, mass loss and distance
• Exploring wind-driving dust species in cool luminous giants I. Basic criteria and dynamical models of M-type AGB stars
• An Infrared Census of DUST in Nearby Galaxies with Spitzer (DUSTiNGS), II. Discovery of Metal-poor Dusty AGB Stars
• Tracing the development of dust around evolved stars: The case of 47 Tuc
• Stellar Exotica in 47 Tucanae
• 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
• Stellar Populations and Mass-Loss in M15: A Spitzer Detection of Dust in the Intra-Cluster Medium
• AGB Sodium Abundances in the Globular Cluster 47 Tucanae (NGC 104)
• The chemical composition of red giants in 47 Tucanae I: Fundamental parameters and chemical abundance patterns
• Ejection of globular cluster interstellar media through ionization by white dwarfs
• A Spitzer search for cold dust within globular clusters
• A peculiar HI cloud near the distant globular cluster Pal 4
• Abundance analysis for long-period variables II. RGB and AGB stars in the globular cluster 47\,Tuc
• A Spitzer Space Telescope survey of extreme Asymptotic Giant Branch stars in M32
• Radiative feedback from ionized gas

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• The ALMA detection of CO rotational line emission in AGB stars in the Large Magellanic Cloud
• The photodissociation of CO in circumstellar envelopes
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• DEATHSTAR: Nearby AGB stars with the Atacama Compact Array II. CO envelope sizes and asymmetries: The S-type stars
• Circumstellar CO in metal-poor stellar winds: the highly irradiated globular cluster star 47 Tucanae V3
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• The Nearby Evolved Stars Survey II: Constructing a volume-limited sample and first results from the James Clerk Maxwell Telescope