Abstract. We present stellar parameters and metallicities for 29 planet-host stars, as well as for a large volume-limited sample of 53 stars not known to be orbited by any planetary-mass companion. These stars add to the results presented in our previous series of papers, providing two large and uniform samples of 119 planet-hosts and 94 "single" stars with accurate stellar parameters and [Fe/H] estimates. The analysis of the results further confirms that stars with planets are metal-rich when compared with average field dwarfs. Important biases that may compromise future studies are also discussed. Finally, we compare the metallicity distributions for single planet-hosts and planet-hosts in multiple stellar systems. The results show that a small difference cannot be excluded, in the sense that the latter sample is slighly overmetallic. However, more data are needed to confirm this correlation.

Aims. This work presents a uniform and homogeneous study of chemical abundances of refractory elements in 101 stars with and 93 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. Methods. 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 16 600 equivalent widths (EW) to calculate the abundances. Results. 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. Conclusions. 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.

Abstract. We present detailed spectroscopic analysis of nitrogen abundances in 31 unevolved metal-poor stars analysed by spectral synthesis of the near-UV NH band at 3360 Å observed at high resolution with various telescopes. We found that [N/Fe] scales with that of iron in the metallicity range −3.1 < [Fe/H] < 0 with the slope 0.01 ± 0.02. Furthermore, we derive uniform and accurate (N/O) ratios using oxygen abundances from near-UV OH lines obtained in our previous studies. We find that a primary component of nitrogen is required to explain the observations. The NH lines are discovered in the VLT/UVES spectra of the very metal-poor subdwarfs G64-12 and LP815-43 indicating that these stars are N rich. The results are compared with theoretical models and observations of extragalactic H II regions and Damped Lyα systems. This is the first direct comparison of the (N/O) ratios in these objects with those in Galactic stars.

We present a detailed and uniform study of oxygen abundances in 155 solar type stars, 96 of which are planet hosts and 59 of which form part of a volume-limited comparison sample with no known planets.

Abstract. We present a detailed and uniform study of C, S, Zn and Cu abundances in a large set of planet host stars, as well as in a homogeneous comparison sample of solar-type dwarfs with no known planetary-mass companions. Carbon abundances were derived by EW measurement of two C  optical lines, while spectral syntheses were performed for S, Zn and Cu. We investigated possible differences in the behaviours of the volatiles C, S and Zn and in the refractory Cu in targets with and without known planets in order to check possible anomalies due to the presence of planets. We found that the abundance distributions in stars with exoplanets are the high [Fe/H]