Research: Stellar variability in the Kepler field
The Kepler space telescope - originally intended to detect extrasolar planets - provides light curves of Sun-like stars, unprecedented in its amount, accuracy and duration. I'm interested in studying (periodic) photometric variability of a large sample of stars. The primary goal is to detect differential rotation in Kepler light curves. The main sources of periodic stellar variability are binarity, pulsations and rotation. The major question is: What can we learn from a light curve about the star itself? Measuring a period in a light curve gives a priori no physical information about its origin! How can we assign this period to the stellar rotation period and how confident can we feel? On the assumption that the flux variations are due to spots on the stellar surface co-rotating with the star, we can apply stellar spot models. This is inevitable since there are many ways to model a given light curve. Necessary parameters such as the (usually unknown) inclination and the stellar latitude result in a high degeneracy of the model. Answering these questions requires a serious error analysis.