Transonic Disk Accretion Revisited

Abstract

Disk accretion of ideal gas with angular momentum is examined under a full relativistic treatment. The rigorous equations of state are used in order to deal properly with the relativistic flow. There appear multiple critical points in some ranges of parameters similar to the polytropic flow. A transition through standing shocks is also examined in relation to the accretion onto a compact star. It is found that for the same parameters and boundary conditions the positions of standing shocks multiply like critical points due to the rotation and relativistic effects. An application to low-mass binary X-ray sources is briefly discussed. In these objects, the very cold transonic flow inside the inner edge of the accretion disk may form the hot atmosphere around a neutron star via shocks.