Stellar rotation, magnetic activity and exoplanets
The faster a cool star rotates, the better its dynamo works and more magnetically active it is. Also, a stellar surface does not rotate as a rigid body, but the different latitudes rotate at different rates. This differential rotation on the other hand is one of the main ingredients in the solar-type dynamos. Thus the stellar rotation rate and the exact rotation pattern over the latitudes are very important in determining how magnetically active the star is. Most cool stars are born as rapid rotators, meaning that in their early lives they are very active. This activity takes many forms (large starspots, flares and coronal mass ejections to name a few), and it can have important implications to exoplanet detectability, formation and habitability. In this talk I will discuss how to measure stellar rotation, what are its effects on magnetic activity and also outline the future investigations connecting all this to exoplanets.