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Start Over Subject barium stars Content Level Research
11. EW of 4 primary stars and the Sun
ID:
ivo://CDS.VizieR/J/MNRAS/476/724
Title:
EW of 4 primary stars and the Sun
Short Name:
J/MNRAS/476/724
Date:
21 Oct 2021
Publisher:
CDS
Description:
Study of primary stars lying in Sirius-like systems with various masses of white dwarf (WD) companions and orbital separations is one of the key aspects to understand the origin and nature of barium (Ba) stars. In this paper, based on high-resolution and high-S/N spectra, we present systematic analysis of photospheric abundances for 18 FGK primary stars of Sirius-like systems including six giants and 12 dwarfs. Atmospheric parameters, stellar masses, and abundances of 24 elements (C, Na, Mg, Al, Si, S, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Sr, Y, Zr, Ba, La, Ce, and Nd) are determined homogeneously. The abundance patterns in these sample stars show that most of the elements in our sample follow the behaviour of field stars with similar metallicity. As expected, s-process elements in four known Ba giants show overabundance. A weak correlation was found between anomalies of s-process elemental abundance and orbital separation, suggesting that the orbital separation of the binaries could not be the main constraint to differentiate strong Ba stars from mild Ba stars. Our study shows that the large mass (>0.51M_{sun}_) of a WD companion in a binary system is not a sufficient condition to form a Ba star, even if the separation between the two components is small. Although not sufficient, it seems to be a necessary condition since Ba stars with lower mass WDs in the observed sample were not found. Our results support that [s/Fe] and [hs/ls] ratios of Ba stars are anti-correlated with the metallicity. However, the different levels of s-process overabundance among Ba stars may not be dominated mainly by the metallicity.
12. HIPPARCOS Ba stars
ID:
ivo://CDS.VizieR/J/A+A/326/722
Title:
HIPPARCOS Ba stars
Short Name:
J/A+A/326/722
Date:
21 Oct 2021
Publisher:
CDS
Description:
HIPPARCOS astrometric and kinematical data together with radial velocities from other sources are used to calibrate both luminosity and kinematics parameters of Ba stars and to classify them. Five distinct classes have been found i.e. some halo stars (H) and four groups belonging to disk population: roughly super-giants (S), two groups of giants (one on the giant branch (G), the other at the clump location(C)) and dwarfs (D). Individual distances and luminosities are estimated.
13. Infrared properties of barium stars
ID:
ivo://CDS.VizieR/J/A+A/372/245
Title:
Infrared properties of barium stars
Short Name:
J/A+A/372/245
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of a systematic survey for IRAS associations of barium stars. A total of 155 associations were detected, and IRAS low-resolution spectra exist for 50 barium stars. We use different color-color diagrams from the visual band to 60{mu}m, relations between these colors and the spectral type, the barium intensity, and the IRAS low-resolution spectra to discuss physical properties of barium stars in the infrared. It is confirmed that most barium stars have infrared excesses in the near infrared. However, a new result of this work is that most barium stars have no excesses in the far infrared. This fact may imply that infrared excesses of barium stars are mainly due to the re-emission of energy lost from the Bond-Neff depression. It is also shown that the spectral type and the barium intensity of barium stars are not correlated with infrared colors, but may be correlated with V-K color.
14. LAMOST-Kepler MKCLASS spectral classification
ID:
ivo://CDS.VizieR/J/AJ/151/13
Title:
LAMOST-Kepler MKCLASS spectral classification
Short Name:
J/AJ/151/13
Date:
21 Oct 2021
Publisher:
CDS
Description:
The LAMOST-Kepler project was designed to obtain high-quality, low-resolution spectra of many of the stars in the Kepler field with the Large Sky Area Multi Object Fiber Spectroscopic Telescope (LAMOST) spectroscopic telescope. To date 101086 spectra of 80447 objects over the entire Kepler field have been acquired. Physical parameters, radial velocities, and rotational velocities of these stars will be reported in other papers. In this paper we present MK spectral classifications for these spectra determined with the automatic classification code MKCLASS. We discuss the quality and reliability of the spectral types and present histograms showing the frequency of the spectral types in the main table organized according to luminosity class. Finally, as examples of the use of this spectral database, we compute the proportion of A-type stars that are Am stars, and identify 32 new barium dwarf candidates.
15. Main-sequence and subgiant Barium stars
ID:
ivo://CDS.VizieR/J/A+A/626/A128
Title:
Main-sequence and subgiant Barium stars
Short Name:
J/A+A/626/A128
Date:
21 Oct 2021
Publisher:
CDS
Description:
Barium (Ba) dwarfs and CH subgiants are the less evolved analogues of Ba and CH giants. They are F- to G-type main-sequence stars polluted with heavy elements by their binary companions when the companion was on the asymptotic giant branch (AGB). This companion is now a white dwarf that in most cases cannot be directly detected. We present a large systematic study of 60 objects classified as Ba dwarfs or CH subgiants. Combining radial-velocity measurements from HERMES and SALT high-resolution spectra with radial-velocity data from CORAVEL and CORALIE, we determine the orbital parameters of 27 systems. We also derive their masses by comparing their location in the Hertzsprung-Russell diagram with evolutionary models. We confirm that Ba dwarfs and CH subgiants are not at different evolutionary stages, and that they have similar metallicities, despite their different names. Additionally, Ba giants appear significantly more massive than their main-sequence analogues. This is likely due to observational biases against the detection of hotter main- sequence post-mass-transfer objects. Combining our spectroscopic orbits with the Hipparcos astrometric data, we derive the orbital inclination and the mass of the WD companion for four systems. Since this cannot be done for all systems in our sample yet (but should be possible with upcoming Gaia data releases), we also analyse the mass-function distribution of our binaries. We can model this distribution with very narrow mass distributions for the two components and random orbital orientations on the sky. Finally, based on BINSTAR evolutionary models, we suggest that the orbital evolution of low-mass Ba systems can be affected by a second phase of interactions along the red giant branch of the Ba star, which impact the eccentricities and periods of the giants.
16. Spectroscopy of NGC 5822-2 and NGC 5822-201
ID:
ivo://CDS.VizieR/J/AJ/146/39
Title:
Spectroscopy of NGC 5822-2 and NGC 5822-201
Short Name:
J/AJ/146/39
Date:
21 Oct 2021
Publisher:
CDS
Description:
Open clusters are very useful examples to explain the constraint of the nucleosynthesis process with the luminosities of stars because the distances of the clusters are better known than those of field stars. We carried out a detailed spectroscopic analysis to derive the chemical composition of two red giants in the young open cluster NGC 5822, NGC 5822-2, and NGC 5822-201. We obtained abundances of C, N, O, Na, Mg, Al, Ca, Si, Ti, Ni, Cr, Y, Zr, La, Ce, and Nd. The atmospheric parameters of the studied stars and their chemical abundances were determined using high-resolution optical spectroscopy. We employed the local thermodynamic equilibrium model atmospheres of Kurucz and the spectral analysis code MOOG. The abundances of the light elements were derived using the spectral synthesis technique. We found that NGC 5822-2 and -201 have, respectively, a mean overabundance of the elements created by the s-process, "s," with the notation [s/Fe] of 0.77+/-0.12 and 0.83+/-0.05. These values are higher than those for field giants of similar metallicity. We also found that NGC 5822-2 and -201 have, respectively, luminosities of 140L_{sun}_ and 76L_{sun}_, which are much lower than the luminosity of an asymptotic giant branch star. We conclude that NGC 5822-2 and NGC 5822-201 are two new barium stars first identified in the open cluster NGC 5822. The mass transfer hypothesis is the best scenario to explain the observed overabundances.
17. Studies of classical barium stars
ID:
ivo://CDS.VizieR/J/AZh/80/704
Title:
Studies of classical barium stars
Short Name:
J/AZh/80/704
Date:
21 Oct 2021
Publisher:
CDS
Description:
The abundances of chemical elements in the atmospheres of seven classical barium stars are derived.
18. Taxonomy of Barium Stars
ID:
ivo://CDS.VizieR/V/81
Title:
Taxonomy of Barium Stars
Short Name:
V/81
Date:
21 Oct 2021
Publisher:
CDS
Description:
Image-tube spectra and photometric observations for 389 bariums stars have been used to determine spectral classification, barium intensity, radial velocity, luminosity, and kinematical properties. The objective of this study is to obtain a homogeneous dataset for analyzing barium characteristics in uniform fashion.
19. UBV Photometry of Barium Stars
ID:
ivo://CDS.VizieR/II/192
Title:
UBV Photometry of Barium Stars
Short Name:
II/192
Date:
21 Oct 2021
Publisher:
CDS
Description:
Magnitudes in V and B-V and U-B colors observed by the 91-cm telescope at Okayama are presented for 109 stars including both classical and marginal barium stars. The two-color diagram shows a fair amount of spread. This can be interpreted by interstellar reddening and variable amounts of line blocking effect. Both classical and marginal barium stars form a fairly homogeneous group.