Paper detail

Rediscussion of eclipsing binaries. Paper IX. The solar-type system KIC 5359678

KIC 5359678 is a 6.231-d period F-type eclipsing binary system whose component stars both show starspot activity. It was observed by the Kepler satellite in long cadence for the full four-year duration of the mission. Wang et al (2021) obtained radial velocity measurements of the two stars and analysed these plus the Kepler data to study their spot activity and measure their physical properties, but left several questions unanswered. We have performed an independent analysis and determined the masses (1.252 +/- 0.018 and 1.065 +/- 0.013 Msun) and radii (1.449 +/- 0.012 and 1.048 +/- 0.017 Rsun) of the stars to high precision. The distance we find to the system is slightly shorter than that from Gaia EDR3 for unknown reason(s). We also investigated the precision of the numerical integration applied to the model light curve to match the 1765-s sampling cadence of the Kepler observations. We found that ignoring this temporal smearing leads to biased radius measurements for the stars: that for the primary is too small by 4 sigma and that for the secondary is too large by 10 sigma. Doubling the sampling rate of the model light curve is sufficient to remove most of this bias, but for precise results a minimum of five samples per observed datapoint is required.