Carbon Stars and Nucleosynthesis in Galaxies

Gustafsson, B.; Ryde, Nils

doi:10.1017/s007418090000276x

Cited by 7 publications

(4 citation statements)

References 60 publications

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“…AGB and post-AGB stars are popular among both theorists and observers because it is during these evolutionary stages that the synthesis and subsequent dredge-up (third mixing) of carbon and heavy s-process metals [1,2] occur. AGB stars are therefore the principal suppliers of heavy metals and important suppliers of carbon and nitrogen to the interstellar medium [3], thereby participating in the chemical evolution of galaxies.…”

Section: Introductionmentioning

confidence: 99%

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Circumstellar envelope manifestations in the optical spectra of evolved stars

Клочкова

2014

Astrophys. Bull.

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We consider the peculiarities of the optical spectra of far evolved stars with circumstellar gaseous-dusty envelopes: the time variability of the absorptionemission profiles of the Hα line, the presence of stationary emission and absorption molecular bands, multicomponent complex profiles of the Na I D-doublet lines. We show that the peculiarities of the line profiles (the presence of an emission component in the Na I D doublet lines, the specific type of the molecular features, the asymmetry or splitting of the profiles of strongest absorptions with low excitation potential of the low level) can be associated with the kinematic and chemical properties of the circumstellar envelope and its morphological type.

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Section: Introductionmentioning

confidence: 99%

“…R CrB type variable, 2 semiregular variable,3 Mira, 4 W Vir type variable in a globular cluster, 5 yellow hypergiant.…”

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confidence: 99%

Circumstellar envelope manifestations in the optical spectra of evolved stars

Клочкова

2014

Astrophys. Bull.

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“…AGB stars and their circumstellar envelopes in general present spherical symmetry (see for example Olofsson 1996). In combination with the thermal pulses and the subsequent third dredge-up, which drags up newly synthesised elements into the atmosphere, the wind causes an enrichment of the interstellar medium in elements synthesised in the AGB star, thus making these stars important actors in the chemical evolution of galaxies (see for example Gustafsson & Ryde 2000). R Dor has a massloss rate of 7 × 10 −8 M yr −1 , which is at the lower end of what is typical for AGB stars, and a wind velocity of 6 km s −1 (Loup et al 1993).…”

Section: Introductionmentioning

confidence: 99%

The 3 spectrum of R Doradus observed with the ISO-SWS

Ryde

Eriksson²

2002

A&A

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Abstract. We have modeled the 2.6-3.7 µm spectrum of the red semiregular variable R Doradus observed with the Short-Wavelength Spectrometer on board the Infrared Space Observatory. The wavelength resolution of the observations varies between R ∼ 2000-2500. We have calculated a synthetic spectrum using a hydrostatic model photosphere in spherical geometry. The agreement between the synthetic spectrum and the ISO observations is encouraging, especially in the wavelength region of 2.8-3.7 µm, suggesting that a hydrostatic model photosphere is adequate for the calculation of synthetic spectra in the near infrared for this moderately varying red giant star. However, an additional absorption component is needed at 2.6-2.8 µm and this discrepancy is discussed. The spectral signatures are dominated by water vapour in the stellar photosphere, but several photospheric OH, CO, and SiO features are also present. The effective temperature and surface gravity derived for R Dor, based on the 2.6-3.7 µm ISO spectrum and the modeling of it with a hydrostatic model photosphere, are 3000 ± 100 K and log g = 0 ± 1 (cgs), respectively. The spectral region observed is found to be temperature sensitive. The effective temperature given here is slightly higher than those reported in the literature. We also discuss possible reasons for this.

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“…Carbon stars are the main producers of s-elements in the Galaxy. They are also significant contributors to 12 C, 13 C and even to rare nuclei such as 7 Li and 26 Al (see e.g., Gustafsson & Ryde 1996;Busso et al 2002). On the other hand, due to their large mass loss rates (10 −8 -10 −4 M ⊙ yr −1 ; Wallerstein & Knapp 1998) many are surrounded by a thick circumstellar envelope.…”

Section: Introductionmentioning

confidence: 99%

Understanding AGB Carbon Star Nucleosynthesis from Observations

Abia

Domı́nguez

Gallino³

et al. 2003

Publ. – Astron. Soc. Aust

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Recent advances in the knowledge of the evolutionary status of asymptotic giant branch (AGB) stars and of the nucleosynthesis processes occurring in them are discussed, and used to interpret abundance determinations for s-process elements, lithium and CNO isotopes in several types of AGB stars. We focus our attention mainly on carbon-rich AGB stars. By combining these different constraints we conclude that most carbon stars in the solar neighborhood are of low mass (M ≤ 3M ⊙ ), their abundances being a consequence of the operation of thermal pulses and the third dredge-up. However, the observed abundances in carbon stars of the R and J types cannot be explained by this standard scenario. These stars may not be on the AGB, but possibly in the core-He burning phases; their envelopes may have been polluted with nuclear ashes of the core-He flash, followed by CNO re-processing enhancing 13 C. Observational evidence suggesting the operation of non-standard mixing mechanisms during the AGB phase is also discussed.

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Carbon Stars and Nucleosynthesis in Galaxies

Cited by 7 publications

References 60 publications

Circumstellar envelope manifestations in the optical spectra of evolved stars

Circumstellar envelope manifestations in the optical spectra of evolved stars

The 3 spectrum of R Doradus observed with the ISO-SWS

Understanding AGB Carbon Star Nucleosynthesis from Observations

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