Spectral Energy Distributions of T Tauri Stars with Passive Circumstellar Disks

We derive hydrostatic, radiative equilibrium models for passive disks surrounding T Tauri stars. Each disk is encased by an optically thin layer of superheated dust grains. This layer reemits directly to space about half the stellar energy it absorbs. The other half is emitted inward and regulates the interior temperature of the disk. The heated disk Ñares. As a consequence, it absorbs more stellar radiation, especially at large radii, than a Ñat disk would. The portion of the spectral energy distribution contributed by the disk is fairly Ñat throughout the thermal infrared. At Ðxed frequency, the contribution from the surface layer exceeds that from the interior by about a factor 3 and is emitted at more than an order of magnitude greater radius. Spectral features from dust grains in the superheated layer appear in emission if the disk is viewed nearly face-on. Subject headings : accretion, accretion disks È circumstellar matter È infrared : stars È radiative transfer È stars : preÈmain-sequence