Chemical analysis of giant stars in the young open cluster NGC 3114^⋆,⋆⋆

¹ Observatório Nacional, Rua José Cristino 77, CEP 20921-400 São Cristóvão Rio de Janeiro, RJ, Brazil
e-mail: osantrich@on.br; claudio@on.br; drake@on.br
² Sobolev Astronomical Institute, St. Petersburg State University, Universitetski pr. 28, 198504 St. Petersburg, Russia

Received: 18 August 2012
Accepted: 9 March 2013

Abstract

Context. Open clusters are very useful targets for examining possible trends in galactocentric distance and age, especially when young and old open clusters are compared.

Aims. We carried out a detailed spectroscopic analysis to derive the chemical composition of seven red giants in the young open cluster NGC 3114. Abundances of C, N, O, Li, Na, Mg, Al, Ca, Si, Ti, Ni, Cr, Y, Zr, La, Ce, and Nd were obtained, as well as the carbon isotopic ratio.

Methods. The atmospheric parameters of the studied stars and their chemical abundances were determined using high-resolution optical spectroscopy. We employed the local-thermodynamic-equilibrium model atmospheres of Kurucz and the spectral analysis code MOOG. The abundances of the light elements were derived using the spectral synthesis technique.

Results. We found that NGC 3114 has a mean metallicity of [Fe/H] = −0.01 ± 0.03. The isochrone fit yielded a turn-off mass of 4.2 M_⊙. The [N/C] ratio is in good agreement with the models predicted by first dredge-up. We found that two stars, HD 87479 and HD 304864, have high rotational velocities of 15.0 km s^-1 and 11.0 km s^-1; HD 87526 is a halo star and is not a member of NGC 3114.

Conclusions. The carbon and nitrogen abundance in NGC 3114 agree with the field and cluster giants. The oxygen abundance in NGC 3114 is lower compared to the field giants. The [O/Fe] ratio is similar to the giants in young clusters. We detected sodium enrichment in the analyzed cluster giants. As far as the other elements are concerned, their [X/Fe] ratios follow the same trend seen in giants with the same metallicity.