Accretion disk boundary layers in classical TTauri stars

The dynamical and thermal structure of an opaque boundary layer, connecting a classical T Tauri star (CTTS: M∗ = 1M , R∗ = 4.3R , Teff = 5000K) with its accretion disk (Ṁ = 10−7M /yr), has been computed, including particularly the effect of a turbulence-driven global heat transport. The inner boundary has been shifted deeper and deeper into the star’s envelope in order to determine how this affects the amount of angular momentum transfer. If the optical depth in the star’s envelope, where the disk meets the star, exceeds in our model example >∼ 10, then there is an energy flux from the star into the boundary layer. For even larger (>∼ 30) optical depths this outward flux approaches the star’s radiation flux and the boundary layer becomes a “hot” one. The angular momentum parameter C alone does not determine the solution uniquely. For a givenC there are, sometimes, two solutions. An argument is given why C ≈ 1.