A search for debris disks with a dual channel adaptive optics imaging polarimeter

Abstract

A dual channel polarimeter was incorporated into the Hokupa'a adaptive optics system mounted on the Gemini North telescope to enhance sensitivity to detecting the light scattered by circumstellar material. The technique suppressed noise introduced by non-repeatable variations of the point spread function which limit the sensitivity of non-simultaneous adaptive optics imaging. Polarimetric images of the classical T-Tauri star environments around GG Tauri Aab, TW Hydrae, LkCa 15, LkHα 242, GM Aurigae, and SR24 N/S were observed to establish the instrument's sensitivity.

A survey of nearby ( d < 25 pc), young ( age < 1 Gyr), solar-analog stars was undertaken with the polarimeter to search for collisionally active debris disks analogous to our young solar system. Of the 24 stars sampled, none were found to have obvious scattered light signatures. Isotropic and Mie scattering model images of debris disks were used to constrain the amount of material around the survey stars to no more than M dust ∼ 10 -2 M Moon of 1-10μ m sized dust contained between 5-50 AU from the sample stars.

Particle lifetimes under the influence of the Poynting Robertson Drag, radiation pressure, and solar wind drag are calculated as a function of central star spectral type. The corpuscular drag from stellar winds shorten dust lifetimes by an amount inversely proportional to the stellar wind mass-loss rate. This translates into dust lifetimes 100-1000 times shorter around young solar analog stars compared to the present day. This effect, cam significantly reduce the near-IR detectability of debris disks around these chromospherically active stars.