Slim Accretion Disks

In a recent paper, Abramowicz, Czerny, Lasota and Szuszkiewicz (1988) have found a new branch of equilibrium solutions for stationary accretion discs around black holes. These solutions correspond to moderately super-Eddington accretion rates. The existence of the new branch is a consequence of cooling due to general relativistic Roche lobe overflow and horizontal advection of heat. On an accretion rate versus surface density plane the new branch forms, together with the two “standard” branches (corresponding to to the Shakura-Sunyaev accretion discs models) a characteristically S-shaped curve. The relation between this “S-curve” and the variability of accretion discs is under study and seems to allow, at least in principle, for a limit cycle behaviour.