Bimodal Accretion Disks: SSD-ADAF Transitions

We show that, unlike the results presented previously in the literature, the transition from an outer Shakura-Sunyaev disk (SSD) to an advectiondominated accretion flow (ADAF) is possible for large values of the viscosity parameter α > 0.5. The transition is triggered by thermal instability of a radiation-pressure-supported SSD. The transition radius is close to the central black hole. We confirm our qualitative prediction by actually constructing global bimodal SSD-ADAF solutions. Subject headings: accretion, accretion disks black hole physics hydrodynamics