Absolute Properties of the Eclipsing Binary Star RT Coronae Borealis

摘要

We present an analysis of existing photometric observations in U, B, and V, and a new light curve in V, as well as spectroscopic observations, of the 5.1 day period, double-lined main-sequence eclipsing binary RT CrB. From the analysis of the light curves and radial velocity curves, we have determined the masses and radii of the components: 1.343 ± 0.010 M⊙ and 2.615 ± 0.04 R⊙ for the primary (hotter) component, 1.359 ± 0.009 M⊙ and 2.946 ± 0.05 R⊙ for the secondary (cooler) component. The formal uncertainties in the masses are both less than 1%, and the formal uncertainties in the radii are both less than 2%. Based on the analyzed light curves, as well as the combined absolute photometry of the system, we estimate effective temperatures of 5781 ± 100 K for the primary component and 5134 ± 100 K for the secondary component, corresponding to spectral types of G5 and K0, respectively. Projected rotational velocities (v sin i) from the spectrograms are measured as 25 ± 2 km s-1 for the primary component and 33 ± 3 km s-1 for the secondary component and are consistent with rotation that is synchronous with the orbital motion. Evolutionary tracks from the current models are in good agreement with the observations for a system of about age 3.5 × 109 yr with a slightly nonsolar chemical composition. We also report an approximate ΔP/P = 3.0 × 10-6 decrease in the orbital period over 37 years.