emulateapjTIME EVOLUTION OF THE MAGNETIC ACTIVITY CYCLE PERIOD . II . RESULTS FOR ANEXPANDED STELLAR

We further explore our new interpretation of the relationships between the magnetic dynamo cycle period P cyc , the rotational period P rot , the activity level (as observed in Ca ii HK), and other stellar properties by expanding the stellar sample beyond that considered in Paper I (Brandenburg, Saar, & Turpin 1998). We do this by adding photometric cycles of active stars and secondaries of CV systems, plus selective addition of less certain cycles in the Mount Wilson HK survey. We also consider the role of stars with two P cyc and long-term trends in their HK or photometric data. We connrm that most stars with age t > 0:5 Gyr occupy two roughly parallel branches, separated by a factor of 6 in P cyc , with ! cyc = / Ro ?0:5 , where Ro is the Rossby number. This result implies that the eeect increases with mean magnetic eld hBi, and that and ! cyc decrease with t along these branches. Stars are not strictly segregated into one or the other branch by activity level, though the low ! cyc = branch is primarily composed of inactive stars. The expanded dataset suggests that for t > 1 Gyr, stars can have ! cyc on one or both branches (double P cyc stars), though among older stars, those with higher mass (F) tend to have their primary P cyc on the low ! cyc = branch, while lower mass (K) stars occupy the high ! cyc = branch. The sun's 80 year Gleissberg cycle agrees with this scenario, suggesting that long-term \trends" in many stars may be segments of long (P cyc 50-100 yr) cycles not yet resolved by the data. Most extremely active stars (P rot < 3 days) appear to occupy a third branch with ! cyc = / Ro 0:4 , suggesting more standard-quenching is operating. There is some evidence that evolved stars may also t the general scheme, lying mostly in a transition region between the two most active branches. We discuss implications for dynamo theory and evolution, and use our results to predict P cyc for stars with long-term trends and a set which appear to be in the stellar analog of the solar Maunder minimum.