The multiplicity of planet host stars - New low-mass companions to planet host stars

Abstract

We present new results from our ongoing multiplicity study of exoplanet host stars, carried out with the infrared camera SofI (Son of ISAAC) at European Southern Observatory-New Technology Telescope (ESO-NTT). We have identified new low-mass companions to the planet host stars HD 101930 and HD 65216. HD 101930 AB is a wide binary system composed of the planet host star HD 101930 A and its companion HD 101930 B which is a M0 to M1 dwarf with a mass of about 0.7 M⊙ separated from the primary by ∼73 arcsec (2200 au projected separation). HD 65216 forms a hierarchical triple system, with a projected separation of 253 au (angular separation of about 7 arcsec) between the planet host star HD 65216 A and its close binary companion HD 65216 BC, whose two components are separated by only ∼0.17 arcsec (6 au of projected separation). Two Very Large Telescope-National Aeronautical Charting Office (VLT-NACO) images separated by 3 yr confirm that this system is comoving to the planet host star. The infrared photometry of HD 65216 B and C is consistent with a M7 to M8 (0.089 M⊙) and a L2 to L3 dwarf (0.078 M⊙), respectively, both close to the substellar limit. An infrared spectrum with VLT-Infrared Spectrometer and Array Camera (VLT-ISAAC) of the pair HD 65216 BC, even though not resolved spatially, confirms this late spectral type. Furthermore, we present H- and K-band ISAAC infrared spectra of HD 16141 B, the recently detected comoving companion of the planet host star HD 16141 A. The infrared spectroscopy as well as the apparent infrared photometry of HD 16141 B are both fully consistent with a M2 to M3 dwarf located at the distance of the planet host star. © 2007 RAS.