CNO behaviour in planet-harbouring stars
I. Nitrogen abundances in stars with planets⋆
1 Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
2 Depto. Astrofísica, Universidad de La Laguna (ULL), 38206 La Laguna, Tenerife, Spain
3 Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP, Rua das Estrelas, 4150-762 Porto, Portugal
4 Departamento de Física e Astronomia, Faculdade de Cîencias, Universidade do Porto, 4169-007 Porto, Portugal
Received: 7 March 2016
Accepted: 23 April 2016
Context. 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.
Aims. 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.
Methods. We used VLT/UVES to obtain high-resolution near-UV spectra of our targets. Spectral synthesis of the NH band at 3360 Å was performed with the spectral synthesis codes MOOG and FITTING.
Results. 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.
Conclusions. We conclude that reliable N abundances can be derived for metal-rich solar type stars from the near UV molecular band at 3360 Å. We confirm a linear trend between [N/Fe] and metallicity expected from standard models of Galactic chemical evolution.
Key words: stars: abundances / stars: chemically peculiar / planetary systems
© ESO, 2016