2026A&A...705A.182M

Context. The physical conditions and processes taking place in the innermost regions of protoplanetary disks are essential for planet formation and general disk evolution. In this context, we study the T-Tauri type young stellar object RY Tau, which exhibits a dust-depleted inner cavity characteristic of a transition disk.
Aims. The goal of this study is to analyze spectrally resolved interferometric observations in the L, M, and N bands of the RY Tau protoplanetary disk obtained with MATISSE. We aim to provide constraints on the spatial distribution and mineralogy of dust in the inner few astronomical units by producing synthetic observations fitting the interferometric observables.
Methods. We employed a 2D temperature gradient disk model to estimate the orientation of the inner disk. Successively, we analyzed the chemical composition of silicates depending on spatial region in the disk. Finally, we sampled the parameter space of a viscous accretion disk model via Monte Carlo radiative transfer simulations to investigate the actual 3D dust density distribution of RY Tau.
Results. We constrained the orientation of the inner disk of RY Tau, finding no evidence of significant misalignment with respect to its outer disk. We identified several silicate species commonly found in protoplanetary disks and observed a depletion of amorphous dust grains toward the central protostar. By simultaneously considering the observed visibilities and the spectral energy distribution (SED), we found that an accretion disk and an optically thin envelope enshrouding the protostar fits the observations best. Radiative transfer simulations show that hot dust close to the protostar and in the line of sight (LOS) to the observer, either in the uppermost disk layers of a strongly flared disk or in a dusty envelope, is necessary to model the observations. The shadow cast by a dense innermost disk midplane on the dust further out explains the observed closure phases in the L band and (to some extent) in the M band. However, the closure phases in the N band are underestimated by our model, hinting at an additional asymmetry in the flux density distribution that is not visible at shorter wavelengths.