THE VERTICAL STRUCTURE OF T TAURI ACCRETION DISKS .1. HEATING BY THE CENTRAL STAR

We present the LTE formal solution for the vertical atmospheric temperature structure of an accretion disk illuminated by its central star. We show that there are two consequences of irradiation: (1) heating of the photospheric layers resulting in continuum radiation, and (2) heating of the optically thin layers resulting in a chromospheric-like temperature increase that may produce disk emission lines in these regions. We illustrate these results by computing the gray vertical temperature structure of a flat accretion disk. Because of the emergent intensity's anisotropy, the observed disk temperature distribution depends on the disk's view angle.