Discovery of a pre-cataclysmic binary with unusual chromaticity of the eclipsed white dwarf by the GPX Survey

Abstract

We report the discovery of a relatively bright eclipsing binary system, which consists of a white dwarf and a main sequence K7 star with clear signs of chromospheric and spot activity. The light curve of this system shows $\sim 0.2$mag ellipsoidal variability with a period of 0.297549d and a short total eclipse of the white dwarf. Based on our analysis of the spectral and photometric data, we estimated the parameters of the system. The K7V star is tidally deformed but does not fill its Roche lobe (the filling factor is about 0.86). The orbital inclination is $i=73^{\circ }.1\pm 0^{\circ }.2$, the mass ratio is $q=M_2/M_1\approx 0.88$. The parameters of the K7V star are $M_2\approx 0.64$M${}_{\odot }$, $R_2=0.645\pm 0.012$R${}_{\odot }$, $T_2\approx 4070$K. The parameters of the white dwarf are $M_1\approx 0.72$M${}_{\odot }$, $R_1=0.013\pm 0.003$R${}_{\odot }$, $T_1=8700\pm 1100$K. Photometric observations in different bands revealed that the maximum depth of the eclipse is in the \textit{SDSS r} filter, which is unusual for a system of a white dwarf and a late main sequence star. We suspect that this system is a product of the evolution of a common envelope binary star, and that the white dwarf accretes the stellar wind from the secondary star (the so-called low-accretion rate polar, LARP).

arXiv comment11 pages 6 figures, accepted for publication in MNRAS

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