Nonlinear Pulsation in the Transonic Region of Geometrically Thin Accretion Disks

Abstract

Nonlinear hydrodynamical simulations are performed to study the evolution of axisymmetric instabilities in viscous accretion disks around a black hole or a nonmagnetized neutron star. When the viscosity parameter α, is sufficiently large (α > 0.05), quasi-periodic pulsations are excited in the innermost transonic region of the disk. Numerical results also show that after the onset of the thermal instability in radiation pressure dominated region, a geometrically thin accretion disk evolves into a slim accretion disk.