Starspot evolution, differential rotation, and correlation between chromospheric and photospheric activities on Kepler-411

We present an analysis of the starspot evolution, the surface differential rotation (SDR), the correlation between chromospheric activity indicators and the spatial connection between chromospheric and photospheric activities on the active star Kepler-411, using time-series photometry over four years fromKepler, and spectroscopic data fromKeck I 10-m and Lijiang 2.4-m telescopes. We constructed the light curve (LC) by re-performing photometry and reduction from the Target Pixel Files and Cotrending Basis Vectors with a manually redefined aperture using the software PYKE3. An efficient program, GEMC LCM, was developed to apply a two-spots model to chosen LC segments with three spot groups at fixed latitudes (30 degrees, 45 degrees), (30 degrees, 60 degrees) and (45 degrees, 60 degrees). We found a periodic variation of the starspots at the period of about 660 d which independs on spot latitudes, and estimated the lower limit of SDR rate alpha = 0.1016(0.0023) and equatoral rotation period P-eq = 9.7810(0.0169) d. Simultaneously, the relative variations of chromospheric activity indicators were derived by subtracting the overall mean spectrum from individual spectrum. It is found that Ca II H and K emissions are strongly correlated with each other, and there also exists a correlation between H alpha and Ca II H & K emissions, with large dispersion, in accordance with previous results. Furthermore, we find the correlation between Ca II H and K emissions is different in 2011 and 2012. The chromospheric emission variation shows a highly spatial anticorrelation with the LC, suggesting a spatial connection between the chromospheric active region and spot region.

Automated summary

This study analyzes the starspot evolution, surface differential rotation, correlation between chromospheric activity indicators, and spatial connection between chromospheric and photospheric activities on the active star Kepler-411. The results show a periodic variation of starspots, strong correlation between Ca II H and K emissions, and spatial anticorrelation between chromospheric emission variation and light curve. Additionally, the study found differences in the correlation between Ca II H and K emissions in different years.