Vol 18, No 10 (2018) / Kjurkchieva

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NSVS 2569022: a peculiar binary among W UMa stars with extremely small mass ratios

Diana P. Kjurkchieva, Velimir A. Popov, Nikola I. Petrov

Abstract

Photometric observations of the W UMa binary NSVS 2569022 are presented. The light curve solution reveals that both components are of F spectral type (temperatures \(T_1 = T_2 = 6100\) K). NSVS 2569022 undergoes a total eclipse of W subtype and the mass ratio is well-determined. Its extremely small value of only 0.077 implies that the target will probably experience instability and a possible merger. This value ranks NSVS 2569022 in sixth place among binaries with the smallest mass ratio. Based on an empirical relation of “period – total mass” for low mass-ratio binaries, we estimate the global parameters of NSVS 2569022: masses \(M_1 = 1.17 M_\odot\) and \(M_2 = 0.09 M_\odot\); radii \(R_1 = 1.19 R_\odot\) and \(R_2 = 0.38 R_\odot\); luminosities \(L_1 = 1.73 L_\odot\) and \(L_2 = 0.17 L_\odot\). An analysis of the characteristics of binaries with extremely low-mass ratios is made. NSVS 2569022 turns out to be a peculiar binary among W UMa stars with extremely small mass ratios due to its unexpectedly small fill-out factor of only 0.014 (slightly overcontact configuration).

Keywords


binaries: eclipsing — binaries: close — stars: fundamental parameters — stars: individual (NSVS 2569022)

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DOI: https://doi.org/10.1088/1674–4527/18/10/129

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