KIC 7284688: A Solar-type Eclipsing Binary with Rapidly Varying O'Connell Effect

We present comprehensive photometric and spectroscopic study of the short-period eclipsing binary KIC 7284688 based on the Kepler, TESS, and LAMOST data. The radial-velocity analysis indicates that it is a triple-lined system composed of a nearly equal-mass binary plus a line-of-sight star. The masses and radii of the components in the binary are measured to be M1 = 1.142 ± 0.020M⊙, R1 = 1.204 ± 0.051R⊙, and M2 = 1.119 ± 0.019M⊙, R2 = 1.149 ± 0.052R⊙. In addition to the eclipses, the light curves of the binary exhibit exhibit rapidly changing O'Connell effect, namely the inequality in light maxima, which could be attributed to the asynchronous rotation of the starspots. We analyzed the variability in the data of light residuals, the difference between light maxima (Max.I−Max.II) as well as the epochs of light minima and determined a rotation period of 0.644 days. Moreover, we detected a quasiperiod with ∼213 days from both the data of (Max.I−Max.II) and light times of minima, which is almost identical to the beat between the rotation period (∼0.644 days) and the orbital period (∼0.646 days). We conclude that the quasiperiodic variations of the O'Connell on the system are probably related to the starspot migration and this is a very rapid variation compared to the magnetic cycles with timescales ranging from years to decades.