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 gsub(rad) = 0.96 and an average value of Asub(rad) = 1.02, while stars with convective envelopes gave an average value of gsub(conv) = 0.31 and an average value of Asub(conv) = 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 gsub(A) = 0.28, while the W-type binaries were found to have both higher average values of gsub(W) = 0.37, and a temperature differential of several hundred degrees, with the secondary being the hotter component. (author)