We have developed a physically self-consistent model of the disk around the nearby 10 Myr old star TW Hya which matches the observed spectral energy distribution and 7mm images of the disk. The model requires both significant dust size evolution and a partially-evacuated inner disk region, as predicted by theories of planet formation. The outer disk, which extends to at least 140 AU in radius, is very optically thick at infrared wavelengths and quite massive (∼ 0.06M ⊙ ) for the relatively advanced age of this T Tauri star. This implies long viscous and dust evolution timescales, although dust must have grown to sizes of order ∼ 1 cm to explain the sub-mm and mm spectral slopes. In contrast, the negligible near-infrared excess emission of this system requires that the disk be optically thin inside ∼ < 4 AU. This inner region cannot be completely evacuated; we need ∼ 0.5 lunar mass of ∼ 1 µm particles remaining to produce the observed 10µm silicate emission. Our model requires a distinct transition in disk properties at ∼ 4 AU, separating the inner and outer disk. The inner edge of the optically-thick outer disk must be heated almost frontally by the star to account for the excess flux at mid-infrared wavelengths. We speculate that this truncation of the outer disk may be the signpost of a developing gap due to the effects of a growing protoplanet; the gap is still presumably evolving because material still resides in it, as indicated by the silicate emission, the molecular hydrogen emission, and by the continued accretion onto the central star (albeit at a much lower rate than typical of younger T Tauri stars). TW Hya thus may become the Rosetta stone for our understanding of the evolution and dissipation of protoplanetary disks.

We present high-resolution, H-band, imaging observations, collected with Subaru/HiCIAO, of the scattered light from the transitional disk around SAO 206462 (HD 135344B). Although previous submm imagery suggested the existence of the dust-depleted cavity at r ≤ 46 AU, our observations reveal the presence of scattered light components as close as 0. ′′ 2 (∼ 28 AU) from the star. Moreover, we have discovered two small-scale spiral structures lying within 0. ′′ 5 (∼ 70 AU). We present models for the spiral structures using the spiral density wave theory, and derive a disk aspect ratio of h ∼ 0.1, which is consistent with previous sub-mm observations. This model can potentially give estimates of the temperature and rotation profiles of the disk based on dynamical processes, independently from sub-mm observations. It also predicts the evolution of the spiral structures, which can be observable on timescales of 10-20 years, providing conclusive tests of the model. While we cannot uniquely identify the origin of these spirals, planets embedded in the disk may be capable of exciting the observed morphology. Assuming that this is the case, we can make predictions on the locations and, possibly, the masses of the unseen planets. Such planets may be detected by future multi-wavelengths observations.

We present the first near-IR scattered light detection of the transitional disk associated with the Herbig Ae star MWC 758 using data obtained as part of the Strategic Exploration of Exoplanets and Disks with Subaru, and 1.1µm HST/NICMOS data. While sub-millimeter studies suggested there is a dustdepleted cavity with r=0. ′′ 35, we find scattered light as close as 0.1 ′′ (20-28 AU) from the star, with no visible cavity at H, K', or K s . We find two small-scaled spiral structures which asymmetrically shadow the outer disk. We model one of the spirals using spiral density wave theory, and derive a disk aspect ratio of h∼0.18, indicating a dynamically warm disk. If the spiral pattern is excited by a perturber, we estimate its mass to be 5 +3 −4 M J , in the range where planet filtration models predict accretion continuing onto the star. Using a combination of non-redundant aperture masking data at L ′ and angular differential imaging with Locally Optimized Combination of Images at K ′ and K s , we exclude stellar or massive brown dwarf companions within 300 mas of the Herbig Ae star, and all but planetary mass companions exterior to 0. ′′ 5. We reach 5-σ contrasts limiting companions to planetary masses, 3-4 M J at 1. ′′ 0 and 2 M J at 1. ′′ 55 using the COND models. Collectively, these data strengthen the case for MWC 758 already being a young planetary system. Subject headings: circumstellar matter instrumentation: high angular resolution polarization planetary systems: protoplanetary disks stars: individual (MWC 758) waves

We present new observations of the far-ultraviolet (FUV; 1100-2200 ) radiation field and the near-to mid-A IR (3-13.5 mm) spectral energy distribution (SED) of a sample of T Tauri stars selected on the basis of bright molecular disks (GM Aur, DM Tau, and LkCa 15). In each source we find evidence for Lya-induced H 2 fluorescence and an additional source of FUV continuum emission below 1700 . Comparison of the FUV spectrå A to a model of H 2 excitation suggests that the strong continuum emission is due to electron impact excitation of H 2 . The ultimate source of this excitation is likely X-ray irradiation that creates hot photoelectrons mixed in the molecular layer. Analysis of the SED of each object finds the presence of inner disk gaps with sizes of a few AU in each of these young (∼1 Myr) stellar systems. We propose that the presence of strong H 2 continuum emission and inner disk clearing are related by the increased penetration power of high-energy photons in gasrich regions with low grain opacity.