Starspot Modulation Detected in the Detached Eclipsing Binary KIC 8301013

Abstract

Abstract We investigate a short-period (P ≈ 4.4 days) eclipsing binary KIC 8301013 using high-quality Kepler photometry and the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) spectroscopic data. Through the light-curve and radial-velocity synthesis using the Wilson–Devinney method, it reveals that the binary is an almost circular (e ≈ 0.001), detached system composed of two late F-type main-sequence stars, with masses and radii of , R 1 = 1.45 ± 0.01R ⊙ and M 2 = 1.11 ± 0.05M ⊙, R 2 = 1.20 ± 0.01R ⊙ for the primary and secondary, respectively. Besides the light variations due to the eclipses, the light curve shows quasi-sinusoidal variations that could be ascribed to starspot modulation. After removing the synthetic binary light curve from the detrended Kepler data, we measure the periods of the active region rotation by using the autocorrelation function (ACF) and Lomb–Scargle periodograms, the decay timescale of the active region by fitting the ACF of out-of-eclipse residuals, and the size of the active region represented by the rms scatter of the out-of-eclipse residuals. The activity level on the binary is significantly stronger than the Sun and has a better agreement with individual F-type stars. No periodic changes are detected in the active region evolution. Thus, KIC 8301013 is an interesting sample for the study of starspot modulation.