The T Tauri star RY Tau as a case study of the inner regions of circumstellar dust disks

TL;DR

This study models the inner circumstellar disk of the T Tauri star RY Tau using interferometric data and spectral analysis, revealing dust evolution and proposing alternative disk structures including an envelope.

Contribution

It introduces a comprehensive modeling approach combining interferometry and spectral data, highlighting the potential role of envelopes and dust evolution in T Tauri disks.

Findings

A flaring disk with accretion explains observations well.

An active disk with an envelope fits data equally well.

Evidence of dust processing with more crystalline particles near the star.

Abstract

We study the inner region of the circumstellar disk around the TTauri star RY Tau. Our aim is to find a physical description satisfying the available interferometric data, obtained with the mid-infrared interferometric instrument at the Very Large Telescope Interferometer, as well as the spectral energy distribution. We also compare the findings with the results of similar studies, including those of intermediate-mass stars. Our analysis is done within the framework of a passive circumstellar disk, which is optionally supplemented by the effects of accretion and an added envelope. To achieve a more consistent and realistic model, we used our continuum transfer code MC3D. In addition, we studied the shape of the 10um silicate emission feature in terms of the underlying dust population, both for single-dish and for interferometric measurements. We show that a modestly flaring disk model with accretion can explain both the observed spectral energy distribution and the mid-infrared visibilities obtained with the mid-infrared infrared instrument. We found an interesting ambiguity: a circumstellar active disk model with an added envelope, and a lower accretion rate than in the active disk model without envelope, could represent the observations equally as well. This type of model with the envelope should be considered a viable alternative in future models of other TTauri stars. The approach of a disk with a puffed-up inner rim wall and the influence of a stellar companion is also discussed. From the study of the silicate emission feature we see evidence for dust evolution in a TTauri star, with a decreasing fraction of small amorphous and an increasing fraction of crystalline particles closer to the star.