The CRIRES Search for Planets Around the Lowest-Mass Stars. II. The Proposed Giant Planet Orbiting VB10 Does Not Exist

摘要

We present high-precision relative radial velocities of the very low-massstar VB10 that were obtained over a time span of 0.61 yr as part of an ongoingsearch for planets around stars at the end of the main sequence. The radialvelocities were measured from high-resolution near-infrared spectra obtainedusing the CRIRES instrument on the VLT with an ammonia gas cell. The typicalinternal precision of the measurements is 10 m/s. These data do not exhibitsignificant variability and are essentially constant at a level consistent withthe measurement uncertainties. Therefore, we do not detect the radial velocityvariations of VB10 expected due to the presence of an orbiting giant planetsimilar to that recently proposed by Pravdo and Shaklan based on apparentastrometric perturbations. In addition, we do not confirm the ~1 km/s radialvelocity variability of the star tentatively detected by Zapatero Osorio andcolleagues with lower precision measurements. Our measurements rule out planetswith M_p > 3 M_Jup and the orbital period and inclination suggested by Pravdoand Shaklan at better than 5 sigma confidence. We conclude that the planetdetection claimed by Pravdo and Shaklan is spurious on the basis of thisresult. Although the outcome of this work is a non-detection, it illustratesthe potential of using ammonia cell radial velocities to detect planets aroundvery low-mass stars.