Production of intermediate-mass and heavy nuclei

Thielemann, Friedrich‐Karl; Fröhlich, C.; Hirschi, Raphaël; Liebendörfer, M.; Dillmann, I.; Mocelj, D.; Rauscher, T.; Martı́nez-Pinedo, G.; Langanke, K.; Farouqi, K.; Kratz, K. L.; Pfeiffer, B.; Panov, I. V.; Nadyozhin, D. K.; Блинников, С. И.; Bravo, Eduardo; Hix, W. R.; Höflich, Peter; Zinner, N. T.

doi:10.1016/j.ppnp.2006.12.019

Cited by 17 publications

(10 citation statements)

References 102 publications

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“…In both instances, the formation of these even-Z iron peak elements occurs in explosive burning of silicon (Hix & Thielemann 1999;Thielemann et al 2007). The isotope 52 Cr, which constitutes 83.8% of the solar Cr abundance, is formed as radioactive 52 Fe mainly in the incomplete Si-burning region (Umeda & Nomoto 2002, 2005.…”

Section: Nucleosynthesismentioning

confidence: 99%

Chromium: NLTE abundances in metal-poor stars and nucleosynthesis in the Galaxy

Bergemann

Cescutti

2010

A&A

157

124

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Aims. We investigate statistical equilibrium of Cr in the atmospheres of late-type stars to ascertain whether the systematic abundance discrepancy between Cr I and Cr II lines, as often found in previous work, is due to deviations from local thermodynamic equilibrium (LTE). Furthermore, we attempt to interpret the Non-LTE (NLTE) trend of [Cr/Fe] with [Fe/H] using chemical evolution models for the solar neighborhood. Methods. NLTE calculations are performed for the model of the Cr atom, comprising 340 levels and 6806 transitions in total. We use the quantum-mechanical photoionization cross-sections of Nahar (2009) and investigate the sensitivity of the model to uncertain crosssections for H I collisions. NLTE line formation is performed for the MAFAGS-ODF model atmospheres of the Sun and 10 metal-poor stars with −3.2 < [Fe/H] < −0.5, and Cr abundances are derived by comparing the synthetic and observed flux spectra. Results. We achieve good ionization equilibrium of Cr for models with different stellar parameters, if inelastic collisions with H I atoms are neglected. The solar NLTE abundance based on Cr I lines is 5.74 dex with σ = 0.05 dex, which is ∼0.1 dex higher than the LTE abundance. For the metal-poor stars, the NLTE abundance corrections to Cr I lines range from +0.3 to +0.5 dex. The resulting [Cr/Fe] ratio is roughly solar for the range of metallicities analyzed here, which is consistent with current views on the production of these iron peak elements in supernovae. Conclusions. The tendency of Cr to become deficient with respect to Fe in metal-poor stars is an artifact caused by the neglect of NLTE effects in the line formation of Cr i, and has no relation to any peculiar physical conditions in the Galactic ISM or deficiencies of nucleosynthesis theory.

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Section: Nucleosynthesismentioning

confidence: 99%

Chromium: NLTE abundances in metal-poor stars and nucleosynthesis in the Galaxy

Bergemann

Cescutti

2010

A&A

157

124

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“…Manganese is produced in both core collapse supernovae (CC SNe) and SNe Ia, but the relative amounts from these two sources are not well constrained. Manganese has one stable isotope, 55 Mn; this element is synthesized as a result of explosive incomplete silicon burning (see, e.g., Thielemann et al 2007 for a more complete discussion). Woosley & Weaver (1995), for example, model nucleosynthesis of massive stars exploding as supernovae of Type II (SNe II) and find increasing Mn yields with increasing metallicity.…”

Section: Introductionmentioning

confidence: 99%

Manganese Abundances in the Globular Cluster Ω Centauri

Cunha

Smith

Bergemann

et al. 2010

ApJ

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We present manganese abundances in 10 red-giant members of the globular cluster ω Centauri; 8 stars are from the most metal-poor population (RGB MP and RGB MInt1) while two targets are members of the more metal rich groups (RGB MInt2 and MInt3). This is the first time Mn abundances have been studied in this peculiar stellar system. The LTE values of [Mn/Fe] in ω Cen overlap those of Milky Way stars in the metal poor ω Cen populations ([Fe/H]∼-1.5 to -1.8), however unlike what is observed in Milky Way halo and disk stars, [Mn/Fe] declines in the two more metal-rich RGB MInt2 and MInt3 targets. Non-LTE calculations were carried out in order to derive corrections to the LTE Mn abundances. The non-LTE results for ω Cen in comparison with the non-LTE [Mn/Fe] versus [Fe/H] trend obtained for the Milky Way confirm and strengthen the conclusion that the manganese behavior in ω Cen is distinct. These results suggest that low-metallicity supernovae (with metallicities ≤ -2) of either Type II or Type Ia dominated the enrichment of the more metal-rich stars in ω Cen. The dominance of low-metallicity stars in the chemical evolution of ω Cen has been noted previously in the s-process elements where enrichment from metalpoor AGB stars is indicated. In addition, copper, which also has metallicity dependent yields, exhibits lower values of [Cu/Fe] in the RGB MInt2 and MInt3 ω Cen populations.

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“…In both instances, the formation of these even-Z iron peak elements occurs in explosive burning of silicon (Hix & Thielemann 1999;Thielemann et al 2007). 52 Cr, which constitutes 83.8% of the solar Cr abundance, is formed as radioactive 52 Fe mainly in the incomplete Si-burning region (Umeda & Nomoto 2002, 2005 Fe are formed as α-particle nuclei, the total yields of Cr and Fe are almost independent of the neutron excess in the matter undergoing explosive burning and, to a first order, of the metallicity of SN progenitors.…”

Section: Nucleosynthesismentioning

confidence: 99%

Chromium: NLTE abundances in metal-poor stars and nucleosynthesis in the Galaxy

Bergemann¹

2011

Proceedings of 11th Symposium on Nuclei in the Cosmos — PoS(NIC XI)

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Aims. We investigate statistical equilibrium of Cr in the atmospheres of late-type stars to show whether the systematic abundance discrepancy between Cr I and Cr II lines, as often encountered in the literature, is due to deviations from LTE. Furthermore, we attempt to interpret the NLTE trend of [Cr/Fe] with [Fe/H] using chemical evolution models for the solar neighborhood. Methods. NLTE calculations are performed for the model of Cr atom, comprising 340 levels and 6806 transitions in total. We make use of the quantum-mechanical photoionization cross-sections of Nahar (2009) and investigate sensitivity of the model to uncertain cross-sections for H I collisions. NLTE line formation is performed for the MAFAGS-ODF model atmospheres of the Sun and 10 metal-poor stars with −3.2 < [Fe/H] < −0.5, and abundances of Cr are derived by comparison of the synthetic and observed flux spectra. Results. We achieve good ionization equilibrium of Cr for the models with different stellar parameters, if inelastic collisions with H I atoms are neglected. The solar NLTE abundance based on Cr I lines is 5.74 dex with σ = 0.05 dex; it is ∼ 0.1 higher than the LTE abundance. For the metal-poor stars, the NLTE abundance corrections to Cr I lines range from +0.3 to +0.5 dex. The resulting [Cr/Fe] ratio is roughly solar for the range of metallicities analyzed here, which is consistent with current views on production of these iron peak elements in supernovae. Conclusions. The tendency of Cr to become deficient with respect to Fe in metal-poor stars is an artifact due to neglect of NLTE effects in the line formation of Cr i, and it has no relation to peculiar physical conditions in the Galactic ISM or deficiencies of nucleosynthesis theory.

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Production of intermediate-mass and heavy nuclei

Cited by 17 publications

References 102 publications

Chromium: NLTE abundances in metal-poor stars and nucleosynthesis in the Galaxy

Chromium: NLTE abundances in metal-poor stars and nucleosynthesis in the Galaxy

Manganese Abundances in the Globular Cluster Ω Centauri

Chromium: NLTE abundances in metal-poor stars and nucleosynthesis in the Galaxy

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