The GRAVITY young stellar object survey -- XV. The star-disk interaction region of the T Tauri star DO Tau

TL;DR

This study combines high-resolution spectroscopy and interferometry to spatially and spectrally resolve the star-disk interaction region of the T Tauri star DO Tau, revealing insights into accretion processes and disk structure.

Contribution

It provides the first combined spectroscopic and interferometric analysis of DO Tau's inner disk and star-disk interaction region, highlighting a potential disk warp and detailed accretion characteristics.

Findings

DO Tau is a strong accretor with variable emission lines.

The Brγ emission region is much smaller than the K-band continuum region.

Inner disk inclination differs from outer disk, indicating possible warp.

Abstract

Protoplanetary disks around young Sun-like stars are the cradles of the vast majority of detected exoplanets. Probing these disks at multiple spatial scales is key to uncovering how planets form. We aim to spatially and spectrally resolve the inner disk and star-disk interaction region of the M0.3 T Tauri star DO Tau by combining two complementary techniques. We used high-resolution near-infrared spectra from CFHT/SPIRou to constrain the magnetospheric star-disk interaction process and optical long-baseline interferometry with ESO VLTI/GRAVITY to determine the sizes of the K-band continuum and Br$\gamma$ line emitting regions. From the SPIRou spectra, we confirmed that this ~0.5 M$_\odot$ star is a strong accretor. The HI and HeI lines exhibit strong variability on a daily timescale, consistent with the burster classification of DO Tau derived from its K2 light curve. We derived an upper limit of 0.35 on the ratio between the magnetospheric truncation radius and the disk corotation radius, indicative of an ordered unstable accretion regime. The size of the Br$\gamma$ line emitting region obtained from GRAVITY is much smaller than the K-band continuum emitting region. This compact Br$\gamma$ emission region ($R_{Br\gamma} \sim$ 0.011 au) suggests that most of the line flux originates from the magnetospheric accretion region and/or from an inner wind close to the magnetosphere-disk interface. The inclination we derived for the inner disk (45-55{\deg}) differs from that of the outer disk inferred from the ALMA continuum (30{\deg}). This points toward a misalignment or warp of the outer disk that may originate from the suspected past encounter with the neighboring HV Tau system.