Recurrent starspot activity and differential rotation in KIC 11560447

TL;DR

This study analyzes starspot activity and differential rotation on the K1IV star in the binary system KIC 11560447 using four years of Kepler data, revealing solar-like differential rotation and recurring starspot emergence patterns.

Contribution

It introduces a method combining maximum entropy reconstruction and phase migration analysis to study surface inhomogeneities and differential rotation in a rapidly rotating sub-giant star.

Findings

Detection of solar-like differential rotation.

Identification of two preferred longitudes of starspot emergence.

Observation of a 0.5 to 1.3-year recurrence period in starspot activity.

Abstract

We present a detailed analysis of surface inhomogeneities on the K1-type sub-giant component of the rapidly rotating eclipsing binary KIC 11560447, using high-precision Kepler light curves spanning nearly four years, corresponding to about 2800 orbital revolutions. We precisely determine the system parameters using high-resolution spectra from the 2.1-m Otto Struve Telescope at the McDonald Observatory. We apply the maximum entropy method to reconstruct the relative longitudinal spot occupancy. Our numerical tests show that the procedure can recover large-scale random distributions of individually unresolved spots, and can track the phase migration of up to three major spot clusters. By determining the drift rates of various spotted regions in orbital longitude, we suggest a way to constrain surface differential rotation and show that the results are consistent with periodograms. The K1IV star exhibits two mildly preferred longitudes of emergence, indications of solar-like differential rotation, and a 0.5 to 1.3-year recurrence period in starspot emergence, accompanied by a secular increase in the axisymmetric component of spot occupancy.