Evolution of Cataclysmic Binaries

Abstract

The minimum period of hydrogen rich cataclysmic binaries at about 80 minutes is due to evolution driven by gravitational radiation. The nature of the gap between 2 and 3 hour periods is less clear. Magnetic braking may be responsible, but this would be in contradiction with the hibernating nova scenario. It is interesting that contact binaries of W UMa type are subject to little or no magnetic braking.