CNO behaviour in planet-harbouring stars. I Nitrogen abundances in stars with planets

TL;DR

This study analyzes nitrogen abundances in 74 solar-type stars, revealing that planet-hosting stars tend to be nitrogen-rich, but this is likely due to their overall higher metallicity, with findings supporting standard Galactic chemical evolution models.

Contribution

It provides the first detailed nitrogen abundance analysis in stars with and without planets using high-resolution near-UV spectra, confirming a linear [N/Fe] vs. [Fe/H] trend.

Findings

Planet hosts are nitrogen-rich compared to single stars.

The nitrogen enrichment correlates with overall metallicity.

Results support standard models of Galactic chemical evolution.

Abstract

Carbon, nitrogen, and oxygen (CNO) are key elements in stellar formation and evolution, and their abundances should also have a significant impact on planetary formation and evolution. We present a detailed spectroscopic analysis of 74 solar-type stars, 42 of which are known to harbour planets. We determine the nitrogen abundances of these stars and investigate a possible connection between N and the presence of planetary companions. We used VLT/UVES to obtain high-resolution near-UV spectra of our targets. Spectral synthesis of the NH band at 3360A was performed with the spectral synthesis codes MOOG and FITTING. We identify several spectral windows from which accurate N abundance can be obtained. Nitrogen distributions for stars with and without planets show that planet hosts are nitrogen-rich when compared to single stars. However, given the linear trend between [N/Fe] vs [Fe/H], this fact can be explained as being due to the metal-rich nature of planet hosts. We conclude that reliable N abundances can be derived for metal-rich solar type stars from the near UV molecular band at 3360A. We confirm a linear trend between [N/Fe] and metallicity expected from standard models of Galactic chemical evolution.