CNO Abundances in Giants with Precise Radial Velocity Measurements (original) (raw)

Abstract

We present oxygen abundances derived from the forbidden oxygen line for G and K giants with precise radial velocity (RV) measurements. Our goal is determine the evolutionary stage for 75 G and K giant stars using CNO abundances. The abundance analysis was done in standard Local Thermodynamic Equilibrium (LTE) with appropriate NLTE corrections and high precision spectra obtained with the FEROS (Setiawan et al. 2003) spectrograph. The fundamental parameters T eff, log g and [Fe/H] were determined from a detailed analysis to obtain the position of stars on the HR diagram as precise as possible. The abundances were derived from a synthetic analysis using plane-parallel, line-blanketed atmospheric models (Kurucz et al. 1993) and an updated version of the spectral analysis code MOOG (Sneden 1973). These abundances offer a unique possibility to establish the evolutionary stage of the objects, specially for those stars presenting a misclassification from the evolutionary tracks. Our stars sample presents three giants with extra solar planets detection HD 47536, HD 122430 and HD 11977 (Figure 1). In addition, derived CNO abundances permit to study the behavior of these elements in low mass (M ≤ 1 − 3.0 M⊙) evolved stars.

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