Yellow giants - A new class of radial velocity variable?

The five K giants and one K supergiant included in a precise (HF) radial velocity program all show significant long-term (about 1 yr), low-amplitude (30-300 m/s rms) radial velocity variations which make them unsuitable as precise radial velocity standards. Arcturus has been discussed in detail elsewhere, and the supergiant Epsilon Peg is probably a semiregular variable. The sampling in the five years of data is inadequate to say whether the giants are related to the Cepheid or Mira variables or form an independent class. The amplitudes of the long-term radial velocity variations of the giants and supergiant are correlated with the level of chromospheric activity shown by K line emission intensity and its fluctuation as seen in He I 10830-A.