Basic elements of the theory of accretion

Abstract

The paper reviews what we consider to be the essential aspects of the theory of accretion. The treatments of accretion of cold gas onto a moving star and of spherical adiabatic accretion are summarized. The formation of specatra in accretion flows onto neutron stars and white dwarfs is described. Spherical accretion onto black holes is treated. Thin accretion disks in the standard α approximation are introduced and the stability conditions for thermal and viscous processes are examined. Thick disks and their stability are briefly treated. The authors offer threads between theory and observations mentioning the astrophysical systems where accretion plays a major role.