The vertical structure of T Tauri accretion discs III. Consistent interpretation of spectra and visibilities with a two-layer model

Abstract

We present a two-layer accretion disc model developed to simultaneously fit optical long baseline visibilities and spectral energy distributions of T Tauri accretion discs. Our model includes viscous heating and absorption of stellar radiation. It analytically expresses the vertical structure of the disc using a two-layer approach: the outer layer is heated by the star and by the inner layer, and the inner layer by visous dissipation and by the outer layer. We compare three prescriptions for the flaring of the irradiated surface, and conclude that a smooth profile with r ~ r^1/8->1/7 has predictions close to those of comparable numerical models. The observables (spectra, images and visibilities) are numerically determined. We study the influence of disc parameters on the structure and observables. Then we apply it to three stars observed in IR interferometry. For T Tau and SU Aur we find a model fit consistent with both visibilities and spectrum but we could not in the case of T Tau North, which might come from caveats in the flux correction from the close South companion. We find that even a single interferometric measurement at one wavelength can bring a very strong constraint on disc models. We predict that future massive interferometric observations will provide a breakthrough in the understanding of accretion disc physics.