Homogeneous abundance analysis of dwarf, subgiant and giant FGK stars with and without giant planets

TL;DR

This study conducts a homogeneous abundance analysis of FGK stars with and without giant planets, revealing differences in element abundances related to stellar evolution and planet hosting, with implications for planetary formation theories.

Contribution

It provides a comprehensive, homogeneous analysis of photospheric parameters and element abundances across different stellar types, linking chemical signatures to planet presence and stellar evolution.

Findings

Giant stars show underabundance in [C/Fe] and overabundance in [N/Fe] and [Na/Fe] due to evolutionary mixing.

Dwarf stars with giant planets are systematically enriched in most elements compared to non-planet hosts.

Planet-hosting stars are significantly overabundant in elements from Mg to Cu when combined, indicating a link between metallicity and planet formation.

Abstract

We have analyzed high-resolution and high signal-to-noise ratio optical spectra of nearby FGK stars with and without detected giant planets in order to homogeneously measure their photospheric parameters, mass, age, and the abundances of volatile (C, N, and O) and refractory (Na, Mg, Si, Ca, Ti, V, Mn, Fe, Ni, Cu, and Ba) elements. Our sample contains 309 stars from the solar neighborhood (up to the distance of 100 pc), out of which 140 are dwarfs, 29 are subgiants, and 140 are giants. The photospheric parameters are derived from the equivalent widths of Fe I and Fe II lines. Masses and ages come from the interpolation in evolutionary tracks and isochrones on the HR diagram. The abundance determination is based on the equivalent widths of selected atomic lines of the refractory elements and on the spectral synthesis of C_2, CN, C I, O I, and Na I features. We apply a set of statistical methods to analyze the abundances derived for the three subsamples. Our results show that: i) giant stars systematically exhibit underabundance in [C/Fe] and overabundance in [N/Fe] and [Na/Fe] in comparison with dwarfs, a result that is normally attributed to evolution-induced mixing processes in the envelope of evolved stars; ii) for solar analogs only, the abundance trends with the condensation temperature of the elements are correlated with age and anticorrelated with the surface gravity, which is in agreement with recent studies; iii) as in the case of [Fe/H], dwarf stars with giant planets are systematically enriched in [X/H] for all the analyzed elements, except for O and Ba (the former due to limitations of statistics), confirming previous findings in the literature that not only iron has an important relation with the planetary formation; and iv) giant planet hosts are also significantly overabundant for the same metallicity when the elements from Mg to Cu are combined together.