Activity and Kinematics of M and L Dwarfs

I discuss observations of two traditional age indicators: chromospheric activity and kinematics, in late-M and L dwarfs near the hydrogen-burning limit. The frequency and strength of chromospheric activity disappears rapidly as a function of temperature over spectral types M8-L4. There is evidence that young late-M and L dwarfs have weaker activity than older ones (the opposite of the traditional stellar age-activity relation). The kinematics of L dwarfs confirm that lithium L dwarfs are younger than non-lithium dwarfs