Analysis of 26 barium stars

Abstract

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]

Mn, Cu, and Zn abundances in barium stars and their correlations with neutron capture elements

“…Additionally, we determined the Mn abundances for the 26 Ba stars analyzed by Allen & Barbuy (2006a), to whom we refer the reader for details on observations and the derivation of atmospheric parameters.…”

“…The abundance results line by line are shown in Table 2, and the average abundances are shown in Table 3. Abundances of Mn that were previously unpublished as well as new calculations for the abundance uncertainties for the 26 stars of Allen & Barbuy (2006a) are also shown in Tables 2 and 3. Details of the sample, the atmospheric parameters, and the abundances derivation are described there.…”

“…Smiljanic et al (2007) and Allen & Barbuy (2006a) employ different methods to obtain the stellar atmospheric parameters T eff , log g, [Fe/H] and microturbulence, so we needed to establish a satisfactory consistence between the two sets of parameters, essentially the T eff scales. Smiljanic et al (2007) rely on the excitation and ionization equilibria of Fe i/Fe ii to derive the parameters self-consistently from the spectroscopic data alone, while Allen & Barbuy (2006a) derive T eff from photometry and the surface gravity from the stellar positions in the HR diagram. Allen & Barbuy (2006a), however, also obtain excitation and ionization T eff values, which agree well with the photometric ones.…”

“…Smiljanic et al (2007) rely on the excitation and ionization equilibria of Fe i/Fe ii to derive the parameters self-consistently from the spectroscopic data alone, while Allen & Barbuy (2006a) derive T eff from photometry and the surface gravity from the stellar positions in the HR diagram. Allen & Barbuy (2006a), however, also obtain excitation and ionization T eff values, which agree well with the photometric ones. Also, Smiljanic et al (2007) compare their spectroscopic surface gravities with those derived from the stellar positions in HR diagrams, and reported excellent agreement between the two surface gravity scales, except for HD 204075, which is the most massive and brightest star of their sample.…”

Abundance analysis of barium and mild barium stars

“…Detailed abundance analyses of barium (or mild barium) stars with modern high quality data are scarce in the literature (Boyarchuk et al 2002;Liang et al 2003;Antipova et al 2004;Yushchenko et al 2004;Allen & Barbuy 2006). Most of the available analyses are based on data with lower S/N ratio (Pilachowski 1977;Smith 1984;Kovacs 1985;Luck & Bond 1991;Zacs 1994).…”