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

L. SuŠrez-Andrťs, G. Israelian, J. I. GonzŠlez HernŠndez, V. Zh. Adibekyan, E. Delgado Mena, N. C. Santos, S. G. Sousa

Abstract
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.

Keywords
stars: abundances, stars: chemically peculiar, planetary systems

Astronomy and Astrophysics
Volume 591, Article Number A69, Number of pages 9
2016 July

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Instituto de Astrof√≠sica e Ci√™ncias do Espa√ßo Universidade do Porto Faculdade de Ciências da Universidade de Lisboa
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia