Context. We present a detailed analysis of 26 barium stars, including dwarf barium stars, providing their atmospheric parameters (T eff , log g, [Fe/H], v t ), and elemental abundances. Aims. We aim at deriving gravities and luminosity classes of the sample stars, in particular to confirm the existence of dwarf barium stars. Accurate abundances of chemical elements were derived. We present the abundance ratios between nucleosynthetic processes, by using Eu and Ba as representatives of the r-and s-processes. Methods. High-resolution spectra were obtained with the FEROS spectrograph at the ESO-1.52 m Telescope, along with photometric data with Fotrap at the Zeiss telescope at the LNA. The atmospheric parameters were derived in an iterative way, with temperatures obtained from colour-temperature calibrations. The abundances were derived using spectrum synthesis for Li, Na, Al, α-, iron-peak, s-, and r-element atomic lines, and for C and N molecular lines. Results. Atmospheric parameters in the range 4300 < T eff < 6500, −1.2 < [Fe/H] < 0.0, and 1.4 ≤ log g < 4.6 were derived, confirming that our sample contains giants, subgiants, and dwarfs. The abundance results obtained for Li, Al, Na, α-, and iron-peak elements for the sample stars show that they are compatible with the values found in the literature for normal disk stars in the same range of metallicities. Enhancements of C, N, and heavy elements relative to Fe, that characterise barium stars, were derived and showed that [X/Ba]

We present a detailed study of carbon-enhanced metal-poor (CEMP) stars, based on high-resolution spectroscopic observations of a sample of 18 stars. The stellar spectra for this sample were obtained at the 4.2 m William Herschel Telescope in 2001 and 2002, using the Utrecht Echelle Spectrograph, at a resolving power R ∼ 52 000 and S /N ∼ 40, covering the wavelength range λλ3700−5700 Å. The atmospheric parameters determined for this sample indicate temperatures ranging from 4750 K to 7100 K, log g from 1.5 to 4.3, and metallicities −3.0 ≤ [Fe/H] ≤ −1.7. Elemental abundances for C, Na, Mg, Sc, Ti, Cr, Cu, Zn, Sr, Y, Zr, Ba, La, Ce, Nd, Sm, Eu, Gd, Dy are determined. Abundances for an additional 109 stars were taken from the literature and combined with the data of our sample. The literature sample reveals a lack of reliable abundance estimates for species that might be associated with the r-process elements for about 67% of CEMP stars, preventing a complete understanding of this class of stars, since [Ba/Eu] ratios are used to classify them. Although eight stars in our observed sample are also found in the literature sample, Eu abundances or limits are determined for four of these stars for the first time. From the observed correlations between C, Ba, and Eu, we argue that the CEMP-r/s class has the same astronomical origin as CEMP-s stars, highlighting the need for a more complete understanding of Eu production.

Aims. Globular clusters are tracers of the history of star formation and chemical enrichment in the early Galaxy. Their abundance pattern can help understanding their chemical enrichment processes. In particular, the iron-peak elements have been relatively little studied so far in the Galactic bulge. Methods. The main aim of this work is to verify the strength of abundances of iron-peak elements for chemical tagging in view of identifying different stellar populations. Besides, the nucleosynthesis processes that build these elements are complex, therefore observational data can help constraining theoretical models, as well as give hints on the kinds of supernovae that enriched the gas before these stars formed.Results. The abundances of iron-peak elements are derived for the sample clusters, and compared with bulge field, and thick disk stars. We derive abundances of the iron-peak elements Sc, V, Mn, Cu, and Zn in individual stars of five bulge globular clusters (NGC 6528, NGC 6553, NGC 6522, NGC 6558, HP 1), and of the reference thick disk/inner halo cluster 47 Tucanae (NGC 104). High resolution spectra were obtained with the UVES spectrograph at the Very Large Telescope over the years.Conclusions. The sample globular clusters studied span metallicities in the range -1.2 < ∼ [Fe/H] < ∼ 0.0. V and Sc appear to vary in lockstep with Fe, indicating that they are produced in the same supernovae as Fe. We find that Mn is deficient in metal-poor stars, confirming that it is underproduced in massive stars; Mn-over-Fe steadily increases at the higher metallicities due to a metallicity-dependent enrichment by supernovae of type Ia. Cu behaves as a secondary element, indicating its production in a weak-s process in massive stars. Zn has an alpha-like behaviour at low metallicities, which can be explained in terms of nucleosynthesis in hypernovae. At the metal-rich end, Zn decreases with increasing metallicity, similarly to the alpha-elements.

Context. Barium stars show enhanced abundances for the slow neutron capture (s-process) heavy elements, so they are suitable objects for studying s-process elements. Aims. The aim of this work is to quantify the contributions of the s-, r-, and p-processes for the total abundance of heavy elements from abundances derived for a sample of 26 barium stars. The abundance ratios between these processes and neutron exposures were studied. Methods. The abundances of the sample stars were compared to those of normal stars, thus identifying the fraction relative to the main component of the s-process. Results. The fittings of the σN curves (neutron-capture cross-section times abundance, plotted against atomic mass number) for the sample stars suggest that the material from the companion asymptotic giant branch star had approximately the solar isotopic composition as concerns fractions of abundances relative to the s-process main component. The abundance ratios of heavy elements, hs, ls, and s and the computed neutron exposure are similar to those of post-AGB stars. For some sample stars, an exponential neutron exposure fits the observed data well, whereas a single neutron exposure provides a better fit for others. Conclusions. The comparison of barium and AGB stars supports the hypothesis of binarity for the barium star formation. Abundances of r-elements that are part of the s-process path in barium stars are usually higher than those in normal stars, so barium stars also seemed to be enriched in r-elements, although to a lower degree than s-elements. No dependence on luminosity classes was found in the abundance-ratio behaviour among the dwarfs and giants of the sample of barium stars.