AAS Meeting #193 - Austin, Texas, January 1999
Session 69. Circumstellar Material
Display, Friday, January 8, 1999, 9:20am-6:30pm, Exhibit Hall 1

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[69.08] Determining the Age of Vega-type stars

Inseok Song, J.P. Caillault (U. Georgia), D. Barrado y Navascues (MPIfA, Heidelberg), J.R. Stauffer (CfA)

We are carrying out a systematic program to determine the ages of Vega-type stars. There have been very few published age estimates, and improving the quantity and the quality of these estimates is extremely important, since they may play an important role in understanding whether planetary system formation is common. If the ages of Vega-type stars are all very young, then this suggests that planet formation is common and that the range of dust optical depths is an age indicator; if the ages are spread out over a few hundred Myr, then planetary formation would be determined by random initial conditions. While it is difficult to determine directly the ages of individual A-stars, it is possible to employ indirect methods, such as standard age-dating techniques for low-mass stars if the A-stars have such binary companions. Our methodology consists of an initial photometric survey, complemented with an extensive search through the literature for proper motions, photometry, and distances of late type companions published in the TYCHO catalog. We have made wide-field photometric observations of ~100 Vega-type stars with the SARA telescope, discovering possible companions for a large fraction of these stars. Spectra of ~40 possible companions were collected with the 60" telescope on Mt. Hopkins. These data allow us to ascertain whether the Vega-type stars and the candidate companions share the same distance, radial velocity, and proper motion, i.e., whether they are coeval. If so, we then determined the ages of confirmed companions through various methods, including the strength of the lithium absorption feature at 6707.8 Å{ } and the location of the star on theoretical evolutionary tracks in the HR diagram.

The author(s) of this abstract have provided an email address for comments about the abstract: song@physast.uga.edu

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