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Description
Currently, the core accretion model has its strongest observational evidence on the chemical signature of mostly main sequence stars with planets. We aim to test whether the well-established correlation between the metallicity of the star and the presence of giant planets found for main sequence stars still holds for the evolved and generally more massive giant and subgiant stars. Although several attempts have been made so far, the results are not conclusive since they are based on small or inhomogeneous samples. We determine in a homogeneous way the metallicity and individual abundances of a large sample of evolved stars, with and without known planetary companions, and discuss their metallicity distribution and trends. Our methodology is based on the analysis of high-resolution echelle spectra (R~67000) from 2-3 meter class telescopes. It includes the calculation of the fundamental stellar parameters (effective temperature, surface gravity, microturbulent velocity, and metallicity) by applying iron ionisation and excitation equilibrium conditions to several isolated FeI and FeII lines, as well as, calculating individual abundances of different elements such as Na, Mg, Si, Ca, Ti, Cr, Co, or Ni.
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