UZ Leo and CV Cyg: two evolved contact binaries

Physical parameters of the W UMa-type eclipsing binaries UZ Leo and CV Cyg are presented based on light-curve analysis. Modified Lucy models (containing either a temperature excess of the secondary component or spots on the surface of the primary) were fitted to V and B light curves. Both systems show either a positive temperature excess (indicating hot secondary) or one large dark spot near the pole of the primary — it is not possible to decide which solution is the real one from the present data sets only. The average density of both systems is less than that of most of the other known W UMa stars; this means that these systems are more evolved, but their mass ratio is considerably smaller than in the case of other evolved contact binaries, which is probably connected with the formation of these systems. The specific angular momenta of both variables are quite large, indicating that these systems may have formed from an originally detached configuration via mass transfer.