The distortion of line profiles and velocities in the spectra of contact binaries.

Use is made of physical models of four contact binary systems, to synthesize line profiles in their spectra. Eclipse and tidal distortion effects displace the profiles at all phases to values which overestimate the stellar velocities while blending effects, when present, tend to produce an opposing displacement. It is shown how erroneous values of mass ratios and orbital elements may be obtained. Comparison with observations bears out these results and also allows absolute values of stellar radii to be obtained. The four systems are placed on the theoretical H-R and mass-luminosity diagrams. Subject headings: line profiles mass-luminosity relation - W Ursae Majoris stars