AAS 205th Meeting, 9-13 January 2005
Session 156 T Tauri Stars and Their Disks
Oral, Thursday, January 13, 2005, 10:00-11:30am, California

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[156.02] Investigating T Tauri Disk Evolution

C. McCabe (JPL), A.M. Ghez (UCLA), L.A. Prato (Lowell Observatory), G. Duchene (Grenoble Observatory)

Using the Keck 10-meter telescope, we have carried out a high spatial resolution mid-infrared (10--20 micron) survey of the inner ~AU region of circumstellar disks around a sample of 69 T Tauri binary stars located in Taurus, Ophiuchus and Corona Australis. These systems have binary separations ranging from 0''25-- 8'' (35--1120 AU). The individual star+disk components are detected in 50 binary systems, increasing the number of spatially resolved T Tauri binaries at 10 micron by a factor of 5. For 38 systems we also have spatially resolved spectroscopic measurements, providing accretion diagnostics, as well as K (2.2 micron)- and L (3.5 micron)- band photometry, either from our own IRTF observations or from the literature. This sample reveals an unexpected population of stars that appear to have inner disk holes. Specifically, ~10% of stars with a mid-infrared excess do not appear to be accreting; in contrast to an actively accreting disk system, these 'passive disks' have significantly lower K-L colors that are, in most cases, consistent with photospheric emission. Two possible explanations for these observed passive disk systems are (1) these stars are in the early phases of transition from an actively accreting, optically thick, disk to an optically thin, non-accreting system, with the disk dispersing in an inside-out manner, or (2) there is a close, unresolved, companion, such as a planet or low mass star, clearing material from the inner edge of the disk and halting the accretion flow.

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© 2004. The American Astronomical Society.