Disk Evolution Study Through Imaging of Nearby Young Stars (DESTINYS): Scattered light detection of a possible disk wind in RY Tau

Abstract

Context. Disk winds are an important mechanism for accretion and disk evolution around young stars. The accreting intermediate-mass T-Tauri star RY Tau has an active jet and a previously known disk wind. Archival optical and new near-infrared observations of the RY Tau system show two horn-like components stretching out as a cone from RY Tau. Scattered light from the disk around RY Tau is visible in the near-infrared, but not seen at optical wavelengths. In the near-infrared, dark wedges separate the horns from the disk, indicating that we may see the scattered light from a disk wind. Aims. We aim to test the hypothesis that a dusty disk wind could be responsible for the optical effect in which the disk around RY Tau is hidden in the I band, but visible in the H band. This could be the first detection of a dusty disk wind in scattered light. We also want to constrain the grain size and dust mass in the wind and the wind-launching region. Methods. We used archived Atacama-Large-Millimetre-Array (ALMA) and Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) I band observations combined with newly acquired SPHERE H band observations and available literature to build a simple geometric model of the RY Tau disk and disk wind. We used Monte Carlo radiative transfer modelling MCMax3D to create comparable synthetic observations that test the effect of a dusty wind on the optical effect in the observations. We constrained the grain size and dust mass needed in the disk wind to reproduce the effect from the observations. Results. A model geometrically reminiscent of a dusty disk wind with small micron to sub-micron-sized grains elevated above the disk can reproduce the optical effect seen in the observations. The mass in the obscuring component of the wind has been constrained to 1 × 10−9 M⊙ ≤ M ≤ 5 × 10−8 M⊙, which corresponds to a mass-loss rate in the wind of about ~1 × 10−8 M⊙ yr−1. Conclusions. A simple model of a disk wind with micron to sub-micron-sized grains elevated above the disk is able to prevent stellar radiation to scatter in the disk at optical wavelengths while allowing photons to reach the disk in the near-infrared. Estimates of mass-loss rate correspond to previously presented theoretical models and points towards the idea that a magneto-hydrodynamic-type wind is the more likely scenario.