April 13

Lucianne Walkowicz (Princeton)

New Light on Stellar Astrophysics with Kepler

Stellar magnetic activity leads to a variety of observable effects, from star spots that modulate the stellar brightness on the order of weeks to months, to flares, which release highly energetic radiation over the course of a few hours. Much of our understanding of these phenomena comes from observations of the Sun, where surface spatial resolution and high time cadence afford us rich detail unavailable for other stars. As studies of stellar spots and flares tend to sample stars that are extremely active, much more so than our Sun, our pictures of solar and stellar cover different regimes and are not yet congruous. The Kepler mission has now obtained nearly three years of precise photometry for stars both like our Sun and considerably different from it. Although Kepler's main goal is the discovery of exoplanets, it has made unprecedented contributions to stellar astrophysics. These new data offer a new chance to not only understand the stars themselves, but to also understand the range of circumstellar habitats in which planets exist. In this talk, I will discuss our ongoing work to characterize the variability due to starspots, stellar rotation and flares in the Kepler planet host stars and the larger sample of targets as a whole.