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

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 HD101930 and HD65216. HD101930AB is a wide binary system composed of the planet host star HD101930A and its companion HD101930B which is a M0 to M1 dwarf with a mass of about 0.7 M_solar separated from the primary by ~73arcsec (2200au projected separation). HD65216 forms a hierarchical triple system, with a projected separation of 253au (angular separation of about 7arcsec) between the planet host star HD65216A and its close binary companion HD65216BC, whose two components are separated by only ~0.17arcsec (6au of projected separation). Two VLT-NACO images separated by 3yr confirm that this system is comoving to the planet host star. The infrared photometry of HD65216B and C is consistent with a M7 to M8 (0.089 M_solar) and a L2 to L3 dwarf (0.078 M_solar), respectively, both close to the substellar limit. An infrared spectrum with VLT-Infrared Spectrometer and Array Camera (VLT-ISAAC) of the pair HD65216BC, even though not resolved spatially, confirms this late spectral type. Furthermore, we present H- and K-band ISAAC infrared spectra of HD16141B, the recently detected comoving companion of the planet host star HD16141A. The infrared spectroscopy as well as the apparent infrared photometry of HD16141B are both fully consistent with a M2 to M3 dwarf located at the distance of the planet host star.

Based on observations obtained on La Silla in ESO programs 075.C-0098(A), 077.C-0572(A) and 078.C-0376(A), as well as on Paranal in ESO programs 070.C-0557(A), 076.C-0057(A) and 078.C-0376(B).

E-mail: markus@astro.uni-jena.de