  Since 1999, a radial velocity survey of 179 red giant stars is ongoing at
Lick Observatory with a one month cadence. At present ~20-100 measurements have
been collected per star with an accuracy of 5 to 8 m/s. Of the stars monitored,
145 (80%) show radial velocity (RV) variations at a level >20 m/s, of which 43
exhibit significant periodicities. Here, we investigate the mechanism causing
the observed radial velocity variations. Firstly, we search for a correlation
between the radial velocity amplitude and an intrinsic parameter of the star,
in this case surface gravity (log g). Secondly, we investigate line profile
variations and compare these with theoretical predictions.
