PI: Stephen E. Strom, NOAO, email@example.com
Address: NIO, 950 North Cherry Ave, Tucson, AZ 85719, United States
CoI: Joan Najita, NOAO
CoI: James Muzerolle, University of Arizona
CoI: Sidney Wolff, NOAO
Title: Understanding the Origin of Transition Disks
Abstract: Transition disks, whose infrared spectral energy distributions reveal the presence of an optically thin inner disk and an optically thick outer disk, are relatively rare, numbering ~1-10% of the population of classical T Tauri stars (cTTS) in nearby star-forming regions. Initially, transition disks were thought to diagnose the onset of a short-lived (10^5yr) ``disk clearing" phase, during which sub- micron size dust in the inner disk agglomerates to form larger grains and ultimately planetesimals. More recently, it has been argued that transition disk SEDs diagnose either (a) a ``gap" carved out by a newly- formed giant planet; or (b) inner disk clearing produced when accretion onto the star is halted by photoevaporation. Which of these scenarios best describes the origin of transition disks? To answer this question, we propose a program aimed at measuring stellar accretion rates based on H(alpha) and Ca II triplet line profiles for a sample of 10 transition disks and 60 classical T Tauri stars in the young cluster IC 348. These measurements will enable us to determine whether transition disks (1) are dominated by rapidly accreting, massive disks, the likeliest candidates for forming giant planets of mass sufficient to open a large inner ``gap"; (2) are dominated instead by slowly accreting, low mass disks susceptible to inner disk clearing by photoevaporation, or (3) span the full range of cTTS accretion rates and masses.
National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360