Stellar parameters and chemical abundances of 223 evolved stars with and without planets

JOFRÉ, EMILIANO; PETRUCCI, ROMINA; SAFFE, CARLOS; SAKER, L.; ARTUR DE LA VILLARMOIS, E.; CHAVERO, CAROLINA; GÓMEZ, MERCEDES; MAUAS, P.

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Lugar: Paris; Año: 2015 vol. 574 p. 1 - 46

0004-6361

Aims. We present fundamental stellar parameters, chemical abundances and rotational velocities for a sample of 86 evolved stars with planets (56 giants; 30 subgiants), as well as for a control sample of 137 stars (101 giants; 36 subgiants) without planets. The analysis was based on both high signal-to-noise and resolution echelle spectra. The main goals of this work are: i) to investigate chemical differences between evolved stars that host planets and those of the control sample without planets; ii) to explore potential differences between the properties of the planet around giants and subgiants and to search for possible correlations between these properties and the chemical abundances of their host stars. Implications for the scenarios of planet formation and evolution are also discussed. Methods. The fundamental stellar parameters (Teff, log g, [Fe/H], xi) were computed homogeneously using the FUNDPAR code. The chemical abundances of 14 elements (Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Zn and Ba) were obtained using the MOOG code. Rotational velocities were derived from the full width at half maximum (FWHM) of iron isolated lines. Results. The [Fe/H] distribution of subgiants with planets is centered at metal-rich values and shows an average excess of 0.16 dex compared to the control sample stars. The [Fe/H] distribution of giants with planets is centered at slightly subsolar metallicities and there is no metallicity enhancement relative to giants without planets. Furthermore, contrary to recent results of Maldonado et al. (2013), we did not find any clear difference between the metallicity distributions of stars with and without planets for giants with Mstar> 1.5 Msun. With regard to the other chemical elements, the analysis of the [X/Fe] distributions show differences between giants with and without planets for some elements, particularly V, Co and Ba. Subgiants with and without planets show similar behavior for most of the elements. On the other hand, we find no evidence for rapid rotation neither among the giants with planets nor among the giants without planets. Finally, analyzing the planet properties, some interesting trends might be emerging: i) multi-planet systems around evolved stars show a slight metallicity enhancement compared with single-planet systems; ii) planets with a < 0.5 AU orbit subgiants with [Fe/H] > 0 and giants hosting planets with a < 1 AU have [Fe/H] < 0; iii) higher-mass planets tend to orbit more metal-poor giants with Mstar < 1.5 Msun, whereas planets around subgiants seem to follow the planet-mass metallicity trend observed on dwarf hosts; iv) [X/Fe] ratios for Na, Si and Al seem to increase with the mass of planets around giants; v) planets orbiting giants show lower orbital eccentricities than those orbiting subgiants and dwarfs, suggesting a more efficient tidal circularization or the result of the engulfment of close-in planets with larger eccentricities.