Abundances of refractory elements in the atmospheres of stars with   extrasolar planets
  This work presents a uniform and homogeneous study of chemical abundances of refractory elements in 101 stars with and 94 without known planetary companions. We carry out an in-depth investigation of the abundances of Si, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Na, Mg and Al. The new comparison sample, spanning the metallicity range -0.70< [Fe/H]< 0.50, fills the gap that previously existed, mainly at high metallicities, in the number of stars without known planets. We used an enlarged set of data including new observations, especially for the field ``single'' comparison stars. The line list previously studied by other authors was improved: on average we analysed 90 spectral lines in every spectrum and carefully measured more than 16600 equivalent widths (EW) to calculate the abundances. We investigate possible differences between the chemical abundances of the two groups of stars, both with and without planets. The results are globally comparable to those obtained by other authors, and in most cases the abundance trends of planet-host stars are very similar to those of the comparison sample. This work represents a step towards the comprehension of recently discovered planetary systems. These results could also be useful for verifying galactic models at high metallicities and consequently improve our knowledge of stellar nucleosynthesis and galactic chemical evolution. 
G. Gilli (1,2), G. Israelian (2), A. Ecuvillon (2), N.C. Santos (3,4)   and M. Mayor (4) ((1) Dipartimento di Astronomia, Un...