Soeren Meibom
Harvard-Smithsonian Center for Astrophysics
 

"The Rotational Evolution of Low-mass Stars"
 

Understanding the evolution of stellar rotation is an integral part of understanding stellar evolution. Star clusters allow us to probe the rotational evolution of late-type stars as a function of the most fundamental stellar properties - mass and age. For cool stars in young open clusters, the rotation period can be measured to very high precision.  Such observations have revealed clear relations between stellar rotation, age, and mass. In this talk, I will present the results of a combination of new stellar rotation periods and extensive information about cluster membership and binarity in the young open clusters M35 and M34. The observations show that late-type members of M35 and M34 are divided into two distinct groups, each with a different dependence of rotation on mass (color). I will discuss these new results in the context of  existing rotation data for late-type stars from the PMS to the Hyades.

The combined results bring new life to the discussion about the internal and external angular momentum transport, the role of magnetic fields, the affect of close companions, and the prospect of determining ages for late-type stars from their rotation and color alone (Gyrochronology). I will outline plans to use the Kepler space mission to push observations of stellar rotation periods beyond the age of the Hyades and the Sun.