Active eclipsing binary RT Andromedae revisited

Abstract

All available photometric and spectroscopic data of the short-period RS CVn-like binary RT And have been reanalyzed in a homogeneous way. The long-term orbital period change is explained by two period jumps, a continuous period decrease combined with the light-time orbit or two light-time orbits. UBVRIJK light curves without maculation effects together with the radial velocities of both components were analysed with the Wilson-Devinney program to compute the photometric and spectroscopic elements and derive the masses of the components: m₁ = 1.10+/-0.02 M_sun and m₂ = 0.83+/-0.02 M_sun. The high orbital inclination i = 87.6degr +/- 0.1degr was confirmed by photoelectric observations of the secondary minimum. The mean observed U light curve shows additional light during the secondary minimum. The small eccentricity found by several authors from the light-curve analysis cannot be ruled out. The face-to-face position of the spots on the surface of both components in 1971 indicates the possibility of a mass transfer from the primary to the secondary component through a magnetic bridge connecting both active regions. Analysis of all available light curves suggests a random position of starspots and does not confirm the idea of active longitude belts. The absolute parameters of the binary together with maximal apparent V brightness set the distance of RT And to 83+/-2 pc, close to the Hipparcos value of 75+/-6 pc.