2025A&A...701A.153S

Aims. This study seeks to determine abundances of neutron-capture elements (Sr, Y, Zr, Ba, La, Ce, Nd, Pr, and Eu) in a large and homogeneous sample of F, G, and K-type planet-host stars (PHSs) located in the northern hemisphere. The sample includes 160 stars, 32 of which are in multi-planetary systems. These stars host a total of 175 high-mass planets and 47 Neptunian and Super-Earth planets. We investigated potential correlations between stellar chemical compositions and the presence of orbiting planets.
Methods. Spectra were obtained using the 1.65-metre telescope at the Moletai Astronomical Observatory and a fibre-fed high-resolution spectrograph covering the entire visible wavelength range (4000-8500 Å). The abundances of neutron-capture elements were determined by differential line-by-line spectrum synthesis using the TURBOSPECTRUM code with the MARCS stellar model atmospheres.
Results. We analysed neutron-capture elements relative to iron ([El/Fe]) and found that the abundances of the majority of chemical elements in exoplanet host stars align with the Galactic chemical evolution. However, [Zr/Fe], [La/Fe], and [Ce/Fe] are overabundant in stars with planets compared to reference stars at a given [Fe/H]. When examining [El/Fe] against planet mass, most elements show positive correlations with higher mass planets, excluding strontium, yttrium, and barium, which exhibit insignificant correlations across all sub-samples. The ∆[El/H] versus T_cond slope distribution shows a positive skewness for planet-hosting stars, suggesting an enrichment of refractory elements compared to analogues. While ∆[El/H]-T_cond slopes and stellar and planetary parameters do not show strong correlations, trends suggest that older dwarf stars with multiple planets have smaller or even negative ∆[El/H]-T_cond slopes compared to younger dwarf stars, which show larger positive slopes. Our results also show that multi-planetary systems are more common around metal-rich stars.