Chemical composition of planetary hosts: II. Abundances of neutron-capture elements

TL;DR

This study analyzes neutron-capture element abundances in 160 planet-host stars, revealing overabundances and correlations with planetary properties, and suggests refractory element enrichment in planet-hosting stars compared to similar stars.

Contribution

It provides a comprehensive, homogeneous analysis of neutron-capture element abundances in a large sample of planet-host stars, highlighting chemical peculiarities and their relation to planetary system characteristics.

Findings

Most neutron-capture elements follow Galactic chemical evolution.

Certain elements like Zr, La, and Ce are overabundant in planet-host stars.

Refractory elements are enriched in planet-host stars compared to analogues.

Abstract

We present a study of neutron-capture element abundances (Sr, Y, Zr, Ba, La, Ce, Nd, Pr, and Eu) in a large and homogeneous sample of 160 F-, G-, and K-type planet-host stars located in the northern hemisphere, including 32 stars in multi-planetary systems. The sample hosts a total of 175 high-mass planets and 47 Neptunian and super-Earth planets. High-resolution spectra were obtained with the 1.65-metre telescope at the Mol\.etai Astronomical Observatory using a fibre-fed spectrograph covering 4000-8500 \r{A}. Elemental abundances were determined by differential line-by-line spectrum synthesis with the TURBOSPECTRUM code and MARCS model atmospheres. The analysis of $[\mathrm{El}/\mathrm{Fe}]$ ratios shows that most elements in PHSs follow the Galactic chemical evolution, but $[\mathrm{Zr}/\mathrm{Fe}]$, $[\mathrm{La}/\mathrm{Fe}]$, and $[\mathrm{Ce}/\mathrm{Fe}]$ are overabundant in PHSs relative to reference stars at a given $[\mathrm{Fe}/\mathrm{H}]$. Correlations between $[\mathrm{El}/\mathrm{Fe}]$ and planet mass are generally positive, except for Sr, Y, and Ba, which show no significant trends. The distribution of $\Delta[\mathrm{El}/\mathrm{H}]$ versus condensation temperature ($T_{\mathrm{cond}}$) slopes is positively skewed for PHSs, indicating enrichment in refractory elements compared to analogues. While no strong correlations are found between $\Delta[\mathrm{El}/\mathrm{H}]$-$T_{\mathrm{cond}}$ slopes and stellar or planetary parameters, older dwarf stars with multiple planets tend to have smaller or negative slopes, whereas younger dwarf stars exhibit larger positive slopes. Our results also confirm that multi-planetary systems are more frequent around metal-rich stars.