Complex Analysis of the Stellar Binary HD25811: A Subgiant System

The visually close binary system HD25811 is analysed to estimate its physical and geometrical parameters in addition to its spectral type and luminosity class. The method depends on obtaining the best fit between the entire observational spectral energy distribution (SED) of the system and synthetic SEDs created by atmospheric modelling of the individual components, consistent with the system's modified orbital elements. The parameters of the individual components of the system are derived as: T a eff = 6850 ± 50 K, T b eff = 7000 ± 50 K, log g a = 4.04 ± 0.10, log g b = 4.15 ± 0.10, R a = 1.96 ± 0.20 R ⊙ , R b = 1.69 ± 0.20 R ⊙ , M a v = 1. m 97 ± 0.20, M b v = 2. m 19 ± 0.20, L a = 7.59 ± 0.70 L ⊙ , L b = 6.16 ± 0.70 L ⊙ with dynamical parallax π (mas)=5.095± 0.095 . The analysis shows that the system consists of a 1.55 M ⊙ F2 subgiant star and a less evolved 1.50 M ⊙ F1 secondary subgiant star with ages around 2 Gy formed by fragmentation. Synthetic magnitudes of both components were calculated under Johnson-Cousins, Strömgren, and Tycho photometrical systems.