Grain Growth and Global Structure of the Protoplanetary Disk Associated with the Mature Classical T Tauri Star, PDS 66

Abstract

We present ATCA interferometric observations of the old (13 Myr), nearby (86 pc) classical T Tauri star (CTTs), PDS 66. Unresolved 3 and 12 mm continuum emission is detected towards PDS 66, and upper limits are derived for the 3 and 6 cm flux densities. The mm data show a spectral slope flatter than that expected for ISM‐sized dust particles, which is most likely a result of grain growth. We also present HST/NICMOS 1.1 μm PSF‐subtracted coronagraphic imaging observations of PDS 66. The HST observations reveal a circumstellar region of dust scattering ∼0.32% of the central starlight, declining in surface brightness as r^(−4.53). The disk is inclined 32±5° from face‐on, and extends to a radius of 170 AU. These data are combined with published optical and longer‐λ observations to make qualitative comparisons between the median Taurus and PDS 66 spectral energy distributions (SEDs). By comparing the near‐infrared emission to a simple model, we det ermine that the location of the inner disk radius is consistent with being at dust sublimation (∼1400 K at 0.1 AU). We place constraints on the mass surface density of the disk at 5 AU assuming a flat‐disk model and find that it is probably too low to form gas giant planets according to current models. Despite the fact that PDS 66 is much older than a typical classical T Tauri star (⩽5 Myr), its physical properties are not much different.

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