On the overstability of axisymmetric oscillations in thin accretion disks

摘要: We examine the stability of geometrically thin and optically thick accretion disks to axisymmetric perturbations. show that standard ..cap alpha..-disk models admit not only classical thermal viscous instabilities, which are generally associated with regions where electron scattering radiation pressure dominant, but also radial pulsational instabilities. derive a general dispersion relationship eigenvectors' response local These results applied for various choices viscosity, opacity equation state. Our indicate there pulsationally overstable regions, otherwise thermally viscously stable. The underlaying physical origin implications these instabilities discussed. Finally, we speculate quasi-periodic oscillation found in dwarf nova systems may be manifestation pulsation overstabilities.