Talk

Using Stellar Surface Maps to Measure Differential Rotation

Rachael Roettenbacher, Yale University

Multiple starspots simultaneously present on cool, active stars sometimes show evidence of rotating with the stellar surface at different rates. These varying rotation rates are assumed to be the result of differential rotation, and the starspots must be located at different stellar latitudes. Differential rotation has been detected with photometric and spectroscopic observations, and parameters to describe the motion can be determined and compared to that of the Sun. Using the longterm photometric light curves from the Kepler satellite, we invert individual rotations of active stars to create maps of evolving, spotted stellar surfaces. We then cross-correlate the stellar surfaces to determine differential rotation parameters, making use of localized starspots and larger-scale photometric variations across the stellar surfaces. We present our findings of differential rotation parameters consistent with theory and those measured by other techniques. We additionally contextualize these findings and the method in the scope of our large-scale study of stellar activity.