Observations and light curve solutions of three WÂ UMa stars with periods of a quarter of a day

Multicolor photometric observations of the W UMa binaries CSS J015638.9+224640, CSS J073801.1+303139 and ROTSE1 J135749.66+361609.3 with periods of around 6 h are presented. The light curve solutions revealed that the components of each target are almost equal in temperature and are of G and K spectral types. CSS J015638.9+224640 and ROTSE1 J135749.66+361609.3 undergo total eclipses and correspondingly they are with well-determined photometric mass ratios. These targets have not only close periods but also close mass ratios (around 0.5), fill-out factors (around 0.2) and component radii. CSS J073801.1+303139 is a slightly overcontact binary with shallow partial eclipses. All three targets are of W subtype. Masses, radii and luminosities of their components were estimated by the empirical relation “period, orbital axis” for short- and ultrashort-period binaries.