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

TL;DR

This study combines interferometric and imaging observations to analyze grain growth and disk structure around the 13-million-year-old T Tauri star PDS 66, revealing evidence of grain growth and a disk possibly too low in mass for gas giant formation.

Contribution

It provides the first detailed multi-wavelength analysis of PDS 66's disk, highlighting grain growth and disk properties in an older classical T Tauri star.

Findings

Evidence of grain growth from spectral slope analysis.

Disk extends to 170 AU with a low total mass.

Inner disk radius matches dust sublimation radius.

Abstract

We present ATCA interferometric observations of the old (13 Myr), nearby (86pc) classical T Tauri star, 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-wave data show a spectral slope flatter than that expected for ISM-sized dust particles, which is evidence of grain growth. We also present HST/NICMOS 1.1 micron PSF-subtracted coronagraphic imaging of PDS 66. The HST observations reveal a bilaterally symmetric circumstellar region of dust scattering about 0.32% of the central starlight, declining radially in surface brightness. The light-scattering disk of material is inclined 32 degrees from face-on, and extends to a radius of 170 AU. These data are combined with published optical and longer wavelength 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 determine that the location of the inner disk radius is consistent with the dust sublimation radius (1400 K at 0.1 AU). We place constraints on the total disk mass using 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.