The Discovery of Stellar Oscillations in the Planet Hosting Giant Star Beta Geminorum

We present the results of a long time series of precise stellar radial velocity measurements of the planet hosting K giant star Beta Geminorum. A total of 20 hours of observations spanning three nights were obtained and the radial velocity variations show the presence of solar-like stellar oscillations. Our period analysis yields six significant pulsation modes that have frequencies in the range of 30 - 150 microHz. The dominant mode is at a frequency of 86.9 microHz and has an amplitude of 5.3 m/s. These values are consistent with stellar oscillations for a giant star with a stellar mass of approximately 2 solar masses. This stellar mass implies a companion minimum mass of 2.6 Jupiter masses. Beta Gem is the first planet hosting giant star in which multi-periodic stellar oscillations have been detected. The study of stellar oscillations in planet hosting giant stars may provide an independent, and more accurate determination of the stellar mass.