A W UMa type system from Southern Hemisphere: CN Hydri

We present an analysis of the Hipparcos photometry and the high-resolution ( λ Δ λ = 41000 ) spectroscopy of the W UMa type system CN Hyi obtained in this study for the first time. The high resolution spectroscopic observations of the system were made at Mt. John University Observatory by using HERCULES fibre-fed échelle spectrograph in September 2007. The radial velocities of the component stars of the system were determined by using the spectral disentangling technique. The orbital solution of CN Hyi yielded the spectroscopic mass ratio as 0.189. We performed the simultaneous solution of the Hipparcos light curve and the radial velocity curves. The light contribution of the third star to the total light of the system was also considered during our photometric analysis. The simultaneous solutions yielded the absolute parameters of the system as M 1 = 1.37 M ⊙ , M 2 = 0.25 M ⊙ for the masses, R 1 = 1.60 R ⊙ , R 2 = 0.77 R ⊙ for the radii, and M V , 1 = 3 m .23, M V , 2 = 4 m .92 for the absolute magnitudes of the primary and secondary components, respectively. The distance of the system was calculated as 56 pc using the distance modulus with the corrections of the interstellar extinction. The positions of the components of CN Hyi in the HR diagram were also discussed.