Observational determination of the gravity darkening exponent and bolometric albedo for close binary star systems

A group of close binary star systems, analysed by the Wilson–Devinney Method, provide observationally determined values for the gravity darkening exponent and the bolometric albedo. Stars with radiative envelopes were found to have an average value of grad = 0.96 and an average value of Arad = 1.02, while stars with convective envelopes gave an average value of gconv = 0.31 and an average value of Aconv = 0.56. For a subgroup composed exclusively of A and W-type W UMa systems, the A-types were found to have a slightly lower average value of gA = 0.28, while the W-type binaries were found to have both higher average values of gW = 0.37, and a temperature differential of several hundred degrees, with the secondary being the hotter component.