Photometric period variation and surface differential rotation in single and binary stars

ABSTRACT We present a comparison of the photometric period variation between five solar-type single stars and five eclipsing binaries possessing solar-type components. Our analyses are based on four years of continuous and high-precision KEPLER photometry. Under the assumption that the photometric period variation carries indirect information about the surface differential rotation (SDR) of the star, our comparison sheds light on the SDR between single and binary member stars. We apply period analysis to the light curves of the single stars. In the case of eclipsing binaries, we first model the spectroscopic orbits and light curves of the target eclipsing binaries. We then remove the model light curve that provides the closest match to the observations from the light curves and obtain the residuals. Finally, we apply photometric period analysis to these residuals to trace the behaviour of the photometric periods of eclipsing binaries in time. Based on the minimum and maximum values of resulting photometric periods, we calculate the relative surface shear, which is accepted as a proxy for the surface differential rotation, of each target. Comparing the relative surface shears, we do not find any notable separation between single and binary stars within our sample. This result suggests that the tidal effects in the binary systems do not appear to suppress the SDR. We also find that the target stars in our sample exhibit larger relative surface shear compared to the giant and sub-giant systems.