Long-Period Radial Velocity Variations in Three K Giants

Precise relative radial velocities were measured for three K giants Alpha Tau, Alpha Boo, and Beta Gem to detect planetary companions. Results reveal strong evidence for long term periodic behavior in the radial velocities: 233 days for Alpha Boo, 643 days for Alpha Tau, and 558 days for Beta Gem. These periods are considered to be too long to be due to radial pulsations. The fact that all three stars exhibit similar periods and give comparable companion masses suggests that the variability is intrinsic to the star (either rotational modulation or pulsations).