SCYON Abstract

Received on January 20 2011

Dust production and mass loss in the Galactic globular cluster 47 Tucanae

Authors	Iain McDonald (¹), M.L. Boyer (²), J.Th. van Loon (³), and A.A. Zijlstra (¹)
Affiliation	(¹) Jodrell Bank Centre for Astrophysics, Alan Turing Building, Manchester, M13 9PL, UK (²) STScI, 3700 San Martin Drive, Baltimore, MD 21218, USA (³) Lennard-Jones Laboratories, Keele University, ST5 5BG, UK
Accepted by	Astrophysical Journal
Contact	mcdonald@jb.man.ac.uk
URL	http://xxx.soton.ac.uk/abs/1101.1096
Links

Abstract

Dust production among post-main-sequence stars is investigated in the Galactic globular cluster 47 Tucanae (NGC 104) based on infrared photometry and spectroscopy. We identify metallic iron grains as the probable dominant opacity source in these winds. Typical evolutionary timescales of AGB stars suggest the mass-loss rates we report are too high. We suggest that this is because the iron grains are small or elongated and/or that iron condenses more efficiently than at solar metallicity. Comparison to other works suggests metallic iron is observed to be more prevalent towards lower metallicities. The reasons for this are explored, but remain unclear. Meanwhile, the luminosity at which dusty mass loss begins is largely invariant with metallicity, but its presence correlates strongly with long-period variability. This suggests that the winds of low-mass stars have a significant driver that is not radiation pressure, but may be acoustic driving by pulsations.