29 research outputs found
Fundamental parameters, integrated RGB mass loss and dust production in the Galactic globular cluster 47 Tucanae
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 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 2000 Lsun. Recent claims of dust
production around lower-luminosity giants cannot be reproduced, despite using
the same archival Spitzer imagery.Comment: 22 pages, 17 figures, accepted ApJ