SCYON Abstract

Received on February 9 2010

Is Dust Forming on the Red Giant Branch in 47 Tuc?

AuthorsMartha L. Boyer (1), Jacco Th. van Loon (2), Iain McDonald (3), Karl D. Gordon (1), Brian Babler (4), Miwa Block (5), Steve Bracker (4), Charles Engelbracht (5), Joe Hora (6), Remy Indebetouw (7), Marilyn Meade (4), Margaret Meixner (1), Karl Misselt (5), Marta Sewilo (1), Bernie Shiao (1), and Barbara Whitney (8)
Affiliation(1) STScI, 3700 San Martin Drive, Baltimore, MD 21218 USA; mboyer@stsci.edu
(2) Astrophysics Group, Lennard-Jones Laboratories, Keele University, Staffordshire ST5 5BG, UK
(3) Jodrell Bank Centre for Astrophysics, Alan Turing Building, University of Manchester, M13 9PL, UK
(4) Department of Astronomy, University of Wisconsin, Madison, 475 North Charter Street, Madison, WI 53706-1582 USA
(5) Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 USA
(6) Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 65, Cambridge, MA 02138-1516 USA
(7) Department of Astronomy, University of Virginia, P.O. Box 3818, Charlottesville, VA 22903-0818 USA
(8) Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301 USA
To appear inApJL, arXiv:1002.1348
Contactmboyer@stsci.edu
URLhttp://
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Abstract

Using Spitzer IRAC observations from the SAGE-SMC Legacy program and archived Spitzer IRAC data, we investigate dust production in 47 Tuc, a nearby massive Galactic globular cluster. A previous study detected infrared excess, indicative of circumstellar dust, in a large population of stars in 47 Tuc, spanning the entire Red Giant Branch (RGB). We show that those results suffered from effects caused by stellar blending and imaging artifacts and that it is likely that no stars below about 1 mag from the tip of the RGB are producing dust. The only stars that appear to harbor dust are variable stars, which are also the coolest and most luminous stars in the cluster.