Name/Affiliation: Sarah Jane Schmidt (Ohio State University)
Towards an Age/Activity Relationship for Ultracool Dwarfs
Despite the large fraction of ultracool dwarfs that show chromospheric activity, the relationship between spectral type, age, and activity at these spectral types is poorly understood. We investigate the chromospheric activity of a large sample of ultracool dwarfs with optical spectra from the Sloan Digital Sky Survey (SDSS). Of the over 12,000 M7-L3 dwarfs with SDSS data, ~6000 have sufficient S/N to classify their activity using the presence and strength of the Ha emission line. We find fraction of active ultracool dwarfs increases from 60% at M7 to 90% at L0, then declines to 70% at L3. We combine these detections of Ha emission with kinematic indicators of age (both Galactic height and three-dimensional velocities) to examine the relationship between activity and age for M7-L3 dwarfs. Our initial results indicate that ultracool dwarfs probably remain active longer than early- to mid-M dwarfs.