Definition and analysis of the fundamental parameters of a close binary system konkoly j064029.1+385652.2

Abstract

In this work, we studied spectroscopic and photometric observations of the close binary system Konkoly J064029.1 + 385652.2, which is a candidate for young pre-cataclysmic variables with an sdO subdwarf. Observations were obtained in 2017–19 on the Large Azimuth Telescope SAO and the Russian–Turkish RTT-150 telescope. The tempera-ture T1eff = 46800 ± 1600 K and surface gravity log g = 6.06 ± 0.11 dex of the primary are determined from modeling optical spectra of KJ 064029 in an era with no reflection effects. These parameters of the star, together with the low atmospheric content of helium He/H = 0.007 ± 0.0007 and other elements, make it more likely to belong to the class of sdO subdwarfs. The orbital inclination angle i = 86.5◦ ± 0.2◦ and the radii of the main (R1 = 0.104 ± 0.008 R⊙) and secondary (R2 = 0.212 ± 0.009 R⊙) were obtained by modeling the light curves in bands V and R. An analysis of the obtained parameters reveals a discrepancy between the dynamic mass of the main primary M1 = 0.567 M⊙ and its estimate based on the evolutionary tracks of hot subdwarfs. This fact leads to the conclusion about the need to clarify the masses of KJ 064029 and the evolutionary status of the primary.