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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[156.01] A Ground-Based Mid-Infrared Imaging Survey of Embedded Young Stellar Objects in the Rho Ophiuchi Cloud Core

M. Barsony (SFSU/Space Science Institute), M.E. Ressler, K.A. Marsh (JPL)

Results of a comprehensive, new, ground-based mid-infrared imaging survey of the young stellar population of the \rho Ophiuchi cloud are presented. Data were acquired at the Palomar 5-m and at the Keck 10-m telescopes with the MIRLIN and LWS instruments, at 0.5\prime\prime and 0.25\prime\prime resolutions, respectively. Of 172 survey objects, 85 were detected. A plot of the frequency distribution of the detected objects with SED spectral slope shows that YSOs spend ~ 3 \times 105 yr in the Flat Spectrum phase, clearing out their remnant infall envelopes. Mid-infrared variability is found among a significant fraction of the surveyed objects and is found to occur for all SED classes with optically thick disks. Large amplitude near-infrared variability, also found for all SED classes with optically thick disks, seems to occur with somewhat higher frequency at the earlier evolutionary stages. The highly variable value of K-band veiling that a single source can exhibit in any of the SED classes in which active disk accretion can take place is striking, and is direct observational evidence for highly time-variable accretion activity in disks. Finallly, by comparing mid-infrared vs. near-infrared excesses in a subsample with well-determined effective temperatures and extinction values, disk clearing mechanisms are explored.

Financial support for this project through NSF grants AST 00-96087 (CAREER), AST 97-53229 (POWRE), and AST 02-06146 is gratefully acknowledged. MB further thanks the NASA/ASEE Summer Faculty Fellowship program at JPL, that made this work possible.

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© 2004. The American Astronomical Society.