SCYON Abstract

Received on January 20 2011

Fundamental parameters, integrated RGB mass loss and dust production in the Galactic globular cluster 47 Tucanae

AuthorsIain McDonald (1), M.L. Boyer (2), J.Th. van Loon (3), A.A. Zijlstra (1), J.L. Hora (4), B. Babler (5), M. Block (6), K. Gordon (2), M. Meade (5), M. Meixner (2), K. Misselt (6), T. Robitaille (4), M. Sewilo (2), B. Shiao (2), and B. Whitney(2)
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
(4) Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 65, Cambridge, MA 02138-1516, USA
(5) Department of Astronomy, University of Wisconsin, Madison, 475 North Charter Street, Madison, WI 53706-1582, USA
(6) Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tuscon, AZ 85721, USA
Accepted byAstrophysical Journal Supplement Series


Fundamental parameters and time-evolution of mass loss are investigated for post-main-sequence stars in the Galactic globular cluster 47 Tucanae (NGC 104). This is accomplished by fitting spectral energy distributions (SEDs) to existing optical and infrared photometry and spectroscopy, to produce a true Hertzsprung–Russell diagram. We confirm the cluster’s distance as d = 4611 (+213/−200) pc and age as 12 +/- 1 Gyr. Horizontal branch models appear to confirm that no more RGB mass loss occurs in 47 Tuc than in the more-metal-poor omega Centauri, though difficulties arise due to inconsistencies between the models. Using our SEDs, we identify those stars which exhibit infrared excess, finding excess only among the brightest giants: dusty mass loss begins at a luminosity of ~1000 Lsun, becoming ubiquitous above L = 2000 Lsun. Recent claims of dust production around lower-luminosity giants cannot be reproduced, despite using the same archival Spitzer imagery.