Innermost parts of accretion disks are thermally and secularly stable

Abstract

There is strong evidence that various types of exotic astronomical objects (quasars, active galactic nuclei, Cyg X-1, SS433) can be explained by accretion disks orbiting black holes. Most of the proposed models of such objects are plagued by instabilities. It is widely held, for example, that all accretion disks must be thermally and secularly unstable in their innermost parts, which seems to be in direct conflict with observations. Much effort has been made to find a stabilizing mechanism operating in the innermost parts of the disks. Here I show that such a mechanism does exist. It is of general relativistic origin, is purely mechanical—operating independently of viscosity and other micro-physical processes—and is similar to the mass loss caused by Roche lobe overflow in close binaries.