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 [Math Processing Error] 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 [Math Processing Error] and [Math Processing Error]; radii [Math Processing Error] and [Math Processing Error]; luminosities [Math Processing Error] and [Math Processing Error]. 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).
binaries: eclipsing — binaries: close — stars: fundamental parameters — stars: individual (NSVS 2569022)
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