LITHIUM AND RAPID ROTATION IN CHROMOSPHERICALLY ACTIVE SINGLE GIANTS

Spectroscopic observations have been obtained of a group of moderately rapidly rotating (v sin i = 6-46 km s-1) chromospherically active, single giants. Such rotational velocities indicate that the rotostat hypothesis of Gray (1989) must be modified. Lithium abundances have been determined for all but one of these stars and for a number of chromospherically active binaries. Many of the single giants have unexpectedly large lithium abundances. The rapid rotation of these single stars, which results in increased chromospheric activity via the dynamo, appears to be related to their high lithium abundances. A scenario is suggested in which the surface convection zone reaches the rapidly rotating core as a star begins its first ascent of the giant branch and dredges up to the surface high angular momentum material and freshly synthesized lithium. The relationship of these single giants to three other groups of stars, the RS Canum Venaticorum binaries, previously identified lithium-rich ''normal'' giants, and FK Comae and suggested related candidates is examined. The properties of many of the stars in these groups appear to be consistent with our scenario. This scenario is an alternative to the coalesced binary theory for many of the proposed FK Comae candidate stars, although not necessarily for FK Com itself.