ROTATION AND ACTIVITY AMONG SOLAR-TYPE STARS OF THE URSA MAJOR GROUP

We examine rotation and chromospheric activity among G and K dwarfs recently shown to be members of the Ursa Major Group (UMaG). Rotation periods for UMaG stars are smaller than for stars of the same colors in the Hyades, and by an amount corresponding to the Skumanich relation (OMEGA is-proportional-to t-1/2, t = age). Most UMaG stars have about the same level of Ca II and K emission, implying that they also have nearly uniform intrinsic rotation rates. That means that the diversity of rotation rates and levels of activity seen among solar-type stars in the alpha Persei and Pleiades clusters (a range of approximately 1.5 dex) has largely converged (to less-than-or-similar-to 0.1 dex) by the age of UMaG (0.3 Gyr).