Improved Age Estimation for Solar‐Type Dwarfs Using Activity‐Rotation Diagnostics

While the strong anticorrelation between chromospheric activity and age has led to the common use of the Ca II H
\nand K emission index (R'_(HK) = L_(HK)/L_(bol)) as an empirical age estimator for solar-type dwarfs, existing activity-age relations
\nproduce implausible ages at both high and low activity levels.We have compiled R'_(HK)
\nHK data from the literature
\nfor young stellar clusters, richly populating for the first time the young end of the activity-age relation. Combining the
\ncluster activity data with modern cluster age estimates and analyzing the color dependence of the chromospheric activity
\nage index,we derive an improved activity-age calibration for F7-K2 dwarfs (0:5…