Asiago eclipsing binaries program

Abstract

The orbit and physical parameters of the previously unsolved double-lined eclipsing binary V570 Per, discovered by the Hipparcos satellite, were derived using high-resolution Echelle spectroscopy and B,V photoelectric photometry. The metallicity from χ 2 analysis of the spectra is (M/H) =+ 0.02 ± 0.03, and reddening from interstellar NaI and KI absorption lines is EB−V = 0.023 ± 0.007. V570 Per is a well-detached system, with shallow eclipses (due to low orbital inclination) and no sign of chromospheric activity. The two components have masses of 1.449 ± 0.006 and 1.350 ± 0.006 Mand spectral types F3 and F5, respectively. They are both still within the main sequence band (T1 = 6842 ± 25 K, T2 = 6562 ± 25 K from χ 2 analysis, R1 = 1.523 ± 0.030, R2 = 1.388 ± 0.019 R� derived by forcing the orbital solution to conform to the spectroscopic light ratio) and are dynamically relaxed to co-rotation with the orbital motion (Vrot,1,2 sini = 40 and 36 (±1) km s −1 ). The distance to V570 Per obtained from the orbital solution is 123 ± 2p c, in excellent agreement with the revised Hipparcos distance of 123 ± 11 pc. The observed properties of V570 Per components were compared to available families of stellar evolutionary tracks and, in particular, to BaSTI models computed on purpose for exactly the observed masses and varied chemical compositions. This system is interesting since both components have their masses in the range where the efficiency of convective core overshooting has to decrease with the total mass as a consequence of the decreasing size of the convective core during the central H-burning stage. Our numerical simulations show that, in order to match all empirical constraints, a small but not null overshooting is required, with efficiencies of λOV = 0.14 and 0.11 for the 1.449 and 1.350 Mcomponents, respectively. This confirms the finding of Paper II on the similar system V505 Per. At the ≈0.8 Gyr age of the system, the element diffusion has reduced the surface metallicity of the models from the initial (M/H) =+ 0.17 to (M/H) =+ 0.02, in perfect agreement with the spectroscopically derived (M/H) =+ 0.02 ± 0.03 value.