- ID:
- ivo://CDS.VizieR/J/A+A/454/895
- Title:
- Abundances of 26 barium stars. I.
- Short Name:
- J/A+A/454/895
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The abundances for Na, Al, alpha-, iron-peak, s-, and r-elements have been derived by using spectrum synthesis for a sample of 26 barium stars, including dwarf barium stars. High-resolution spectra were obtained with the FEROS spectrograph at the ESO-1.52m Telescope, along with photometric data with Fotrap at the Zeiss telescope at the LNA.
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- ID:
- ivo://CDS.VizieR/J/A+A/454/917
- Title:
- Abundances of 26 barium stars. II.
- Short Name:
- J/A+A/454/917
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 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 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 s. The fittings of the sigmaN 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.
- ID:
- ivo://CDS.VizieR/J/A+A/533/A51
- Title:
- Abundances of 12 metal-rich barium stars
- Short Name:
- J/A+A/533/A51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We determined the atmospheric parameters and abundance pattern for a sample of metal-rich barium stars. We used high resolution optical spectroscopy. Atmospheric parameters and abundances were determined using the local thermodynamic equilibrium atmosphere models of Kurucz and the spectral analysis code MOOG. We show that the stars have enhancement factors, [s/Fe], from 0.25 to 1.16. Their abundance pattern of Na, Al, {alpha}-elements and iron group elements as well as their kinematical properties are similar to the characteristics of the other metal rich and super metal-rich stars already analyzed. We conclude that metal rich barium stars do not belong to the bulge population. We also show that metal rich barium stars are useful targets to probe the s-process enrichment in high metallicity environments.
- ID:
- ivo://CDS.VizieR/J/AZh/82/601
- Title:
- Abundances of 4 red giants
- Short Name:
- J/AZh/82/601
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the Na, Mg, Al, and Si abundances in the atmospheres of more than 40 stars, including red giants of different spectral subgroups (normal red giants, mild and classical barium stars) and several supergiants. All these elements exhibit abundance excesses, with the overabundance increasing with the star's luminosity. The dependence of the overabundances for each of these elements on the luminosity (or logg) is the same for all the spectral subgroups, testifying to a common origin: they are all products of hydrogen burning in the NeNa and MgAl cycles that have been dredged up from the stellar interiors to the outer atmospheric layers by convection that gradually develops during the star's evolution from the main sequence to the red-giant stage. The sodium abundances derived for several stars are lower than for other stars with similar atmospheric parameters. The ages and kinematic characteristics of these two groups of stars suggest that they probably belong to different stellar generations.
- ID:
- ivo://CDS.VizieR/J/A+A/319/881
- Title:
- Ba II strength of barium stars
- Short Name:
- J/A+A/319/881
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The absolute magnitude of barium stars has been obtained from kinematical data using a new algorithm based on the maximum-likelihood principle. The method allows to separate a sample into groups characterized by different mean absolute magnitudes, kinematics and z-scale heights. Three groups belonging to the disk population have been obtained. We give, for each star of these three groups, the probability P of belonging to each of them and the assignation to the most likely one (G). The first column gives an an identification number: for most of the stars HD numbers are given, otherwise BD numbers. The following two columns present the spectral type taken from the INCA database and the strength of the BaII line (I_Ba) taken from Lu catalogue (1991) <V/81>.
- ID:
- ivo://CDS.VizieR/J/A+A/626/A127
- Title:
- Barium and related stars and WD companions
- Short Name:
- J/A+A/626/A127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper provides long-period and revised orbits for barium and S stars adding to previously published ones. The sample of barium stars with strong anomalies comprise all such stars present in the Lu et al. catalogue. We find orbital motion for all barium and extrinsic S stars monitored. We obtain the longest period known so far for a spectroscopic binary involving an S star, namely 57 Peg with a period of the order of 100-500yr. We present the mass distribution for the barium stars, which ranges from 1 to 3M_{sun}_, with a tail extending up to 5M_{sun}_ in the case of mild barium stars. This high-mass tail comprises mostly high-metallicity objects ([Fe/H]>=-0.1). Mass functions are compatible with WD companions and we derive their mass distribution which ranges from 0.5 to 1 Msun. Using the initial - final mass relationship established for field WDs, we derived the distribution of the mass ratio q'=M_AGB,ini_/M_Ba_ (where M_AGB,ini_ is the WD progenitor initial mass, i.e., the mass of the system former primary component) which is a proxy for the initial mass ratio. It appears that the distribution of q' is highly non uniform, and significantly different for mild and strong barium stars, the latter being characterized by values mostly in excess of 1.4, whereas mild barium stars occupy the range 1-1.4. We investigate as well the correlation between abundances, orbital periods, metallicities, and masses (barium star and WD companion). The 105 orbits of post-mass-transfer systems presented in this paper pave the way for a comparison with binary-evolution models.
- ID:
- ivo://CDS.VizieR/J/A+A/321/L9
- Title:
- Barium stars in the HR diagram
- Short Name:
- J/A+A/321/L9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table2 is an extension of Table 1 to 15 additional stars with slightly less accurate parallaxes (see text). The entries are the same in both tables.
- ID:
- ivo://CDS.VizieR/J/AZh/79/909
- Title:
- Chemical abundances in barium stars
- Short Name:
- J/AZh/79/909
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used high-resolution spectra to compute model atmospheres to derive the atmospheric abundances of moderate barium stars. Comparing our results with analogous data for normal red giants, we find that the moderate barium stars appear to not differ systematically from normal red giants. Their chemical abundance anomalies show the same patterns and can be interpreted in terms of evolutionary effects: the evolutionary stage, mass, luminosity, and metallicity of the objects.
- ID:
- ivo://CDS.VizieR/J/A+A/397/257
- Title:
- Chemical compositions of four barium stars
- Short Name:
- J/A+A/397/257
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Chemical compositions of four barium stars are studied. We obtain their {alpha}, iron peak and neutron-capture (n-capture) process element abundances. The atomic data and measured equivalent widths (EWs) of the related spectral lines are given. The abundance errors caused by the combined effects of the uncertainties in oscillator strengths loggf-values, equivalent widths (EWs) and stellar atmospheric parameters (e.g. effective temperature Teff, surface gravity logg, and microturbulent velocity {xi_t_}) are the total abundance uncertainties. The individual and total abundance uncertainties caused by these factors are given.
- ID:
- ivo://CDS.VizieR/J/A+A/608/A100
- Title:
- CMD and mass distribution of Ba stars
- Short Name:
- J/A+A/608/A100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- With the availability of parallaxes provided by the Tycho-Gaia Astrometric Solution, it is possible to construct the Hertzsprung-Russell diagram (HRD) of barium and related stars with unprecedented accuracy. A direct result from the derived HRD is that subgiant CH stars occupy the same region as barium dwarfs, contrary to what their designations imply. By comparing the position of barium stars in the HRD with STAREVOL evolutionary tracks, it is possible to evaluate their masses, provided the metallicity is known. We used an average metallicity [Fe/H]=-0.25 and derived the mass distribution of barium giants. The distribution peaks around 2.5M_{sun}_, with a tail at higher masses up to 4.5M_{sun}_. This peak is seen as well in the mass distribution of a sample of normal K and M giants used for comparison and is associated with stars located in the red clump. When we compare these mass distributions, we see a deficit of low-mass (1-2M_{sun}_) barium giants. This is probably because low-mass stars reach large radii at the tip of the red giant branch, which may have resulted in an early binary interaction. Among barium giants, the high-mass tail is however dominated by stars with a barium index (based on a visual inspection of the barium spectral line) less than unity, i.e., with a very moderate barium line strength. We believe that these stars are not genuine barium giants, but rather bright giants (or supergiants) where the barium lines are strengthened because of a positive luminosity effect. Moreover, contrary to previous claims, we do not see differences between the mass distributions of mild and strong barium giants.
