Analysis of W UMa systems. I. The A-type systems.

An analysis of seven A-type W UMa eclipsing binary stars using the Wilson-Devinney computer code is presented. The objectives were (1) determination of accurate values of the bolometric albedo, gravity darkening exponent, and linear limb darkening coefficients for these systems, and (2) analyzing light curves from several epochs to detect system parameter changes in three stars. It was shown that a gravity darkening exponent is preferred by the systems in this sample; the linear darkening coefficients show systematic deviations from the theoretical values predicted by stellar atmosphere models, and a wide range of values of the bolometric albedo A is indicated.