The absolute magnitudes of the barium stars.

Junqueira

2003

A&A

Abstract. We present the abundance pattern of two CH subgiant stars HD 50264 and HD 87080 based on high-resolution optical spectra. We also determined the spectroscopic stellar atmospheric parameters, temperature and microturbulent velocity as well We compare the abundance pattern with abundances of disk stars and also with other stars of the same class. We found that iron group, α-elements, manganese, as well as sodium and aluminum of HD 50264 and HD 87080 follow the abundance pattern of the disk stars. The heavy-element abundance pattern of both stars shows enhancements by a factor of 4-6 with respect to the sun. By heavy-element we mean the elements that have been synthesized by neutron capture, such as barium, yttrium and zirconium. We also discuss the abundances of the s-process elements and compare our results with other binary systems that display enrichment due to neutron-capture reactions, through several diagrams involving the index [hs/ls] and [s/Fe], the metallicity and [C/Fe] ratio. We compare the observed abundance of the heavy elements with theoretical nucleosynthesis calculations. This shows that the s-process are best fit by models in which the seed nuclei are exposed to single neutron irradiation and with a neutron exposure of τ = 0.9 and τ = 1.0 respectively for HD 50264 and HD 87080. We also use the [Rb/Zr] ratio in order to investigate how this ratio behaves versus metallicity for other binary systems, including HD 50264 and HD 87080 that are s-process enriched.

Section: Determination Of the Atmospheric Parameterssupporting

confidence: 89%

Spectroscopic analysis of two CH subgiant stars: HD 50264 and HD 87080

Junqueira

2003

A&A

“…In field stars, the percentage of barium stars is only 1 (MacConnell et al 1972). In open clusters, the binary frequency of red giant spectroscopic binaries with periods less than 4000 days is 23% (Mermilliod & Mayor 1990).…”

Section: Heavy Elements: Neutron-capture Elementsmentioning

confidence: 98%

“…HD 65314 was also selected as an s-process-enriched comparison star after analyzing our results for the stellar parameters and abundances obtained from the large high-resolution spectroscopic survey of the barium stars selected from the samples of MacConnell et al (1972) and Bidelman (1981) as well as some stars from Gomez et al (1997). This survey aims to obtain the atmospheric parameters, abundances, and the kinematical properties of these chemically peculiar stars and compare them with the non-sprocess-enriched giant stars.…”

Section: Atmospheric Parametersmentioning

confidence: 99%

Two Barium Stars in the Open Cluster NGC 5822

Santrich

Castro

2013

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 140 L and 76 L , 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.

“…• 3668 were made by MacConnell et al (1972), Catchpole et al (1977), Lu et al (1983), and Lu (1991) using a prism spectrograph with a dispersion of 50 Å mm −1 at Hγ . All these studies were unable to constrain its luminosity class, and for some stars (MacConnell et al 1972;Catchpole et al 1977) not even their spectral types.…”

Section: Previous Observations Of Bd−03mentioning

confidence: 99%

“…Motivated by the questions mentioned above, we started a high-resolution spectroscopic survey of the barium stars from the MacConnell et al (1972) and Bidelman (1981) samples. Among about 230 stars surveyed, we discovered a new CH subgiant, BD−03…”

Section: Introductionmentioning

confidence: 99%

High-Resolution Spectroscopic Observations of a New Ch Subgiant Star: Bd–03°3668

The Astronomical Journal

Драке²

2011

This work reports on the discovery of a new CH subgiant star BD−03• 3668 with a significant overabundance of the elements created by s-process nucleosynthesis, such as barium and lead. Its atmospheric parameters and abundance pattern are determined by employing the local thermodynamic equilibrium model atmospheres of Kurucz using the spectral analysis code MOOG. Due to the low luminosity of this star, the s-process overabundance is better explained by mass transfer from an asymptotic giant branch star in the past.