1994PASP..106..161S

Archived data for 23 M13 giants, from the extensive series of Lick Hamilton Echelle studies of globular giants by Kraft, Sneden, Langer, et al., are analyzed for radial velocities and strong line core displacements. Of several giants in this program which were observed more than once, only III-73 was found to have significant radial velocity variations. However, when the Lick velocities are combined with the extensive set of velocities determined a decade earlier by Lupton et al. (1987), the stars L598, IV-25, III-56, II-90, III-73, and I-48 show differences > 4.0 km/sec which may reflect long-term variability or binary reflex motions. Displaced cores are found with increasing frequency as stars approach the tip of the giant branch. This suggests that mass outflow increases with increasing luminosity along the giant branch. Time variations are seen in core displacements of IV-25 and III-56.