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

Vadim Krushinsky, Paul Benni, Artem Burdanov, Igor Antokhin, Eleonora Antokhina, Emmanuël Jehin, Khalid Barkaoui, Alan Fitzsimmons, Christopher Gibson, Michaël Gillon, Alexander Popov, Özgür Baştürk, Zouhair Benkhaldoun, Alessandro Marchini, Riccardo Papini, Fabio Salvaggio, Varvara Brazhko

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Abstract

We report the discovery of a relatively bright eclipsing binary system, which consists of a white dwarf (WD) and a main-sequence K7 star with clear signs of chromospheric and spot activity. The light curve of this system shows ∼0.2 mag ellipsoidal variability with a period of 0.297549 d and a short total eclipse of the WD. 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 = 73.1° ± 0.2°, and the mass ratio is q = M2/M1 ≈ 0.88. The parameters of the K7V star are M2 ≈ 0.64 M⊙, R2 = 0.645 ± 0.012R⊙, and T2 ≈ 4070 K. The parameters of the WD are M1 ≈ 0.72 M⊙, R1 = 0.013 ± 0.003R⊙, and T1 = 8700 ± 1100 K. Photometric observations in different bands revealed that the maximum depth of the eclipse is in the SDSS r filter, which is unusual for a system of a WD 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 WD accretes the stellar wind from the secondary star (the so-called low-accretion-rate polar, hereafter LARP).
Original languageEnglish
Pages (from-to)5208-5217
JournalMonthly Notices of the Royal Astronomical Society
Volume493
Issue number4
Early online date27 Feb 2020
DOIs
Publication statusPublished - 01 Apr 2020

Keywords

  • binaries: close
  • binaries: eclipsing
  • stars: low-mass
  • white dwarfs

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