ECCENTRIC-MODE EXCITATION OF ACCRETION DISKS

The development of eccentric-mode resonances in accretion discs within binary systems is simulated. The measured rotational rates of the res ulting eccentric discs are found to agree with the observed superhump periods of SU UMa stars. This lends support to the eccentric-disc mode l of superhump formation. In addition, the decline of the superhump pe riod is found to be explained by the inwards propagation of the eccent ric mode. Measurements of superhump periods therefore constrain both t he mass ratio of a system and the structure of its accretion disc.