Related papers: Surface abundances of OC supergiants
A project which aims to understand the abundance patterns of He, C, N, O, Ne, S, and Ar for a small sample of planetary nebulae is described. Abundance ratios of O/H, C/O, and N/O especially show a broad range relative to their solar…
The formation of [O I], O I and OH lines in metal-poor stars has been studied by means of 3D hydrodynamical model atmospheres. For O I detailed 3D non-LTE calculations have been performed. While the influence of 3D model atmospheres is…
We aim to provide new empirical clues about macroturbulent spectral line broadening in O- and B-type stars to evaluate its physical origin. We use high-resolution spectra of ~430 stars with spectral types in the range O4-B9 (all luminosity…
The super-Earth exoplanet 55 Cnc e, the smallest member of a five-planet system, has recently been observed to transit its host star. The radius estimates from transit observations, coupled with spectroscopic determinations of mass, provide…
We present carbon and oxygen abundances for 941 FGK stars-the largest such catalog to date. We find that planet-bearing systems are enriched in these elements. We self-consistently measure C/O, which is thought to play a key role in planet…
Recently an increasing number of studies were devoted to measure the abundances of neutron-capture elements heavier than iron in stars belonging to Galactic Open Clusters (OCs). OCs span a sizeable range in metallicity -0.6<[Fe/H]<+0.4),…
Based on a simple, but fairly successful, model of the chemical evolution of the Milky Way disk, we study the evolution of the abundances of the elements He, C, N, O, Ne, Mg, Al, Si, S, Ar and Fe. We use metallicity dependent yields for…
Lithium and zirconium abundances (the latter taken as representative for s-process enrichment) are determined for a large sample of massive Galactic O-rich AGB stars, for which high resolution optical spectroscopy has been obtained…
Utilizing the observational data of 55,318 star-forming galaxies (SFGs) selected from the catalog of MPA-JHU emission-line measurements for the SDSS DR8, we investigate the galaxy downsizing effect of their O and N enrichments, and the…
Building upon earlier observations which demonstrate substantial star-to-star differences in the carbon abundances of M13 subgiants, we present new Keck LRIS spectra reaching more that 1.5 mag below the M13 main-sequence turn-off (to V ~…
The distribution of stellar abundances along the Galactic disk is an important constraint for models of chemical evolution and Galaxy formation. In this study we derive radial gradients of C, N, O, Mg, Al, Si, as well as S, from abundance…
We present deep high-resolution (R~15,000) and high-quality UVES optical spectrophotometry of nine planetary nebulae with dual-dust chemistry. We compute physical conditions from several diagnostics. Ionic abundances for a large number of…
The AF-supergiants in the Galaxy and the SMC allow us to examine predictions from evolution models through their CNO abundances. In these proceedings, we recalculate the NLTE nitrogen abundances in 22 Galactic and 9 SMC A-supergiants using…
The relative abundances of carbon and oxygen have long been recognized as fundamental diagnostics of stellar chemical evolution. Now, the growing number of exoplanet observations enable estimation of these elements in exoplanetary…
The dependence of stellar molecular bands on the metallicity is studied using infrared L-band spectra of AGB stars (both carbon-rich and oxygen-rich) and M-type supergiants in the Large and Small Magellanic Clouds (LMC and SMC) and in the…
We present an analysis of high-resolution spectra of six core-helium-burning "clump" stars in the open cluster NGC 6134. Atmospheric parameters T_eff, log_g, v_t, and [Fe/H] were determined in our previous study by Carretta et al. (2004).…
A study of the O/Fe ratio in metal-poor main sequence and subgiant stars is presented using the [OI] 6300A line, the OI 7774A triplet, and a selection of weak FeII lines observed on high-resolution spectra acquired with the VLT UVES…
We present oxygen abundances for 72 F and G dwarf stars in the solar neighbourhood. Using the kinematics of the stars we divide them into two sub-samples with space velocities that are typical for the thick and thin disks, respectively. The…
We have calculated the evolution of low metallicity red giant stars under the assumption of deep mixing between the convective envelope and the hydrogen burning shell. We find that the extent of the observed abundance anomalies, and in…
Aims: Recent observations have challenged our understanding of rotational mixing in massive stars by revealing a population of fast-rotating objects with apparently normal surface nitrogen abundances. However, several questions have arisen…