SV CENTAURI — A TRULY CONTACT BINARY

A light-curve-synthesis program which implements interpolation in a grid of nongray model atmospheres has been used to determine the geometrical elements of SV Cen by simultaneous differentialcorrection fitting of the three-color light curves obtained in UBV by Irwin and Landolt (1972). Solutions with the mass ratio fixed at its spectroscopie value of 0.84 reveal an extraordinarily high degree of contact between the components (fill-out parameter ƒ = 0.10 ± 0.02) and a rather high temperature of the less massive component relative to the more massive component. The large local temperature excess of the secondary star, X = ∆T/T = 0.78 ± 0.03 (which results in temperatures 28,000° and 17,000°K, for the less massive and more massive compounds, respectively) is difficult to understand in the framework of the contact model but might be related to the thermal -time-scale mass-transfer stage of the evolution of SV Cen.