KIC 5359678: a detached eclipsing binary with starspots

We study the detached eclipsing binary, KIC 5359678, with starspot modulation using the high-quality Kepler photometry and LAMOST spectroscopy. The PHOEBE model, optimal for this binary, reveals that this system is a circular detached binary, composed of two F-type main-sequence stars. The masses and radii of the primary and the secondary are M-1 = 1.31 +/- 0.05 M-circle dot, R-1 = 1.52 +/- 0.04 R-circle dot, M-2 = 1.12 +/- 0.04 M-circle dot, and R-2 = 1.05 +/- 0.06 R-circle dot, respectively. The age of this binary is estimated to be about 2 Gyr, a value much longer than the synchronization time-scale of 17.8 Myr. The residuals of light curves show quasi-sinusoidal signals, which could be induced by starspots. We apply autocorrelation function analysis on the out-of-eclipse residuals and find that the spot with rotational period close to the orbital period, while, the decay time-scale of starspots is longer than that on the single stars with the same temperature, period range, and rms scatter. A two-starspot model is adopted to fit the signals with two-dip pattern, whose result shows that the longitude decreases with time.

Automated summary

In this study, the detached eclipsing binary system KIC 5359678 is analyzed using high-quality Kepler photometry and LAMOST spectroscopy. The system is found to consist of two F-type main-sequence stars, with estimated masses, radii, and age. Signs of starspot modulation are observed, and a model with two starspots is applied to fit the signals, showing a decrease in longitude over time.