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We have been monitoring 373 very bright (V < 6 mag) G and K giants with highprecision optical Doppler spectroscopy for more than a decade at LickObservatory. Our goal was to discover planetary companions around those starsand to better understand planet formation and evolution aroundintermediate-mass stars. However, in principle, long-term, g-mode nonradialstellar pulsations or rotating stellar features, such as spots, couldeffectively mimic a planetary signal in the radial velocity data. Our goal isto compare optical and infrared radial velocities for those stars with periodicradial velocity patterns and to test for consistency of their fitted radialvelocity semiamplitudes. Thereby, we distinguish processes intrinsic to thestar from orbiting companions as reason for the radial velocity periodicityobserved in the optical. Stellar spectra with high spectral resolution havebeen taken in the H-band with the CRIRES near-infrared spectrograph at ESO'sVLT for 20 stars of our Lick survey. Radial velocities are derived using manydeep and stable telluric CO2 lines for precise wavelength calibration. We findthat the optical and near-infrared radial velocities of the giant stars in oursample are consistent. We present detailed results for eight stars in oursample previously reported to have planets or brown dwarf companions. All eightstars passed the infrared test. We conclude that the planet hypothesis providesthe best explanation for the periodic radial velocity patterns observed forthese giant stars.

Precise radial velocities of giant stars VIII. Testing for the presence of planets with CRIRES Infrared Radial Velocities