AAS 202nd Meeting, May 2003
Session 24 When Do Planets Form?
Topical Oral, Tuesday, May 27, 2003, 8:30-10:00am and 10:45am-12:30pm, 204

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[24.09] Do gas disks persist once the emission from circumstellar dust disappears?

J.S. Bary, D.A. Weintraub (Vanderbilt University), J.H. Kastner (Rochester Institute of Technology)

Infrared excesses and millimeter emission observed towards T Tauri stars (TTS) emerged as the initial evidence proving that many young sun-like stars are surrounded by disks of circumstellar material. However, the largest and possibly the most important component of the disk, H2, has remained virtually undetected. Therefore, disk lifetimes are not estimated by the disappearance of H2 emission, but by the absence of emission from the dust and various trace molecules of gas such as CO. Our high resolution spectroscopic observations of classical and weak-line TTS challenge the notion that the absence of tracer emission from dust and gas signifies that a star is devoid of all circumstellar material. Having detected H2 in the disks of several cTTS and at least one wTTS, we suggest that previous interpretations related to the presence of disks around young stars lacking detectable emission from trace constituents should be reconsidered. The disappearance of emission from the dust and CO emission alternatively may signify that planet building is proceeding successfully within the disk. Therefore, disk lifetimes determined merely by the absence of such emissions may be too short. Dust and gas may persist in the disk sufficiently long enough for planets to form, possibly on a timescale of 10~Myr. Possible stimulation mechanisms responsible for producing the observed ro-vibrational H2 emission will be reviewed and their significance for the location and total mass of H2 residing in the disk, which are crucial to the interpretation of our data, will be discussed.

The author(s) of this abstract have provided an email address for comments about the abstract: jeffrey.s.bary@vanderbilt.edu

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Bulletin of the American Astronomical Society, 35 #3
© 2003. The American Astronomical Soceity.