The Chromospheric Activity and Ages of M Dwarf Stars in Wide Binary Systems

We investigate the relationship between age and chromospheric activity for139 M dwarf stars in wide binary systems with white dwarf companions. The ageof each system is determined from the cooling age of its white dwarf component.The current limit for activity-age relations found for M dwarfs in openclusters is 4 Gyr. Our unique approach to finding ages for M stars allows forthe exploration of this relationship at ages older than 4 Gyr. The generaltrend of stars remaining active for a longer time at later spectral type isconfirmed. However, our larger sample and greater age range reveals additionalcomplexity in assigning age based on activity alone. We find that M dwarfs inwide binaries older than 4 Gyr depart from the log-linear relation for clustersand are found to have activity at magnitudes, colors and masses which arebrighter, bluer and more massive than predicted by the cluster relation. Inaddition to our activity-age results, we present the measured radial velocitiesand complete space motions for 161 white dwarf stars in wide binaries.Comment: 22 pages including 9 figures and 5 tables. Accepted for publication in The Astronomical Journa