AN OBSERVATIONAL PERSPECTIVE OF TRANSITIONAL DISKS AROUND T TAURI STARS
C. Espaillat (Harvard-Smithsonian Center for Astrophysics, Cambridge, United States),
S. Andrews (Harvard-Smithsonian Center for Astrophysics, Cambridge, United States),
N. Calvet (University of Michigan, United States),
P. D'Alessio (Instituto de Astronomiia, UNAM, Mexico),
J. Hashimoto (National Astronomical Observatory of Japan, Japan),
A. Kraus (Institute for Astronomy, Hawaii, United States),
S. Kraus (Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, United States),
J. Muzerolle (Space Telescope Science Institute, United States),
J. Najita (National Optical Astronomy Observatory, United States),
Z. Zhu (Princeton University, United States)
Disks around T Tauri stars (TTS) are thought to be the sites of planet formation. However, many questions
exist concerning how the gas and dust in the disk evolve into a planetary system. Observations of
TTS may provide insights and there are some objects in particular that have gained increasing attention
in this regard. These objects contain inner holes in their disks and have been dubbed transitional
disks (TDs). Some have speculated that planets are responsible for carving out the holes in these TDs
and that they are in transition between protoplanetary disks and post-planet building disks (i.e., debris
disks). Spitzer produced detailed spectral energy distributions (SEDs) that allowed us to infer the radial
structure of TDs in some detail, and also pointed to the diversity of TD systems. The growing sample
of TDs opened up the possibility of demographic studies, which are providing unique insights. More
recently, Spitzer results have stimulated work with other facilities. There now exist sub-millimeter and
near-infrared (NIR) images that confirm large cavities in TDs. In addition, potential protoplanets have
been detected in some of these disks. TDs are the strongest link to planet formation around TTS to
date and are a key area to study if further progress is to be made on understanding the initial stages
of planet formation. Here we will look at key observational properties constraining the dust and gas
properties of TDs and compare them to the main disk clearing mechanisms proposed to date (i.e.,
photoevaporation, grain growth, and planets).
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