  We report the analysis of a binary blue straggler in NGC 6752 with a short
orbital period of 0.315 d and a W UMA-type light curve. We use photometric data
spanning 13 years to place limits on the mass ratio (0.15<q<0.35), luminosity
ratio (L1/L2 about 4.0) and the ratio of the radii of the components (r1/r2
about 2.0). The effective temperatures of the components are nearly identical,
and the system is detached or semi-detached (in the latter case the component
filling its Roche lobe is the secondary). Such a configuration is unusual given
the shortness of the orbital period, and it must have resulted from substantial
mass exchange. We suggest that some secondaries of W UMa-type stars, normally
regarded as main sequence objects which fill their Roche lobes to different
degrees, in fact may be shell-burning cores of originally more massive
components.
