THE ORBITAL PERIOD OF AM CANUM-VENATICORUM

We report the discovery of a strictly periodic signal at 1028.7325 +/- 0.0004 s in the light curve of the cataclysmic variable AM Canum Vena ticorum. This brings to an end the long search for the true binary per iod of this important star, which represents the latest known stage of binary star evolution. It provides a more secure and quantitative bas is for testing theories of binary evolution. And it provides strong ev idence in favor of the ''permanent superhump'' interpretation of this star and other cataclysmic variables of extreme mass ratio.