Nucleosynthesis of Zinc and Iron Peak Elements in Population III Type II Supernovae: Comparison with Abundances of Very Metal Poor Halo Stars

Umeda, Hideyuki; Nomoto, Ken’ichi

doi:10.1086/323946

Cited by 540 publications

(664 citation statements)

References 66 publications

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“…Various attempts have been made with standard SN II events (e.g., Woosley & Weaver 1995), zero-metallicity SN II events, including pair-instability SN (e.g., Heger & Woosley 2002), varying the mass-cut (dividing the mass expelled from that falling back onto the remnant) (e.g., Nakamura et al 1999), hypernovae (i.e. very energetic SNe, with E > 10 52 erg) or varying the SN explosion energy (e.g., Nakamura et al 2001;Umeda & Nomoto 2002, 2005.…”

Section: Discussionmentioning

confidence: 99%

Extremely metal-poor stars in classical dwarf spheroidal galaxies: Fornax, Sculptor, and Sextans

Tafelmeyer

Jablonka

Hill

et al. 2010

A&A

152

287

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We present the results of a dedicated search for extremely metal-poor stars in the Fornax, Sculptor, and Sextans dSphs. Five stars were selected from two earlier VLT/Giraffe and HET/HRS surveys and subsequently followed up at high spectroscopic resolution with VLT/UVES. All of them turned out to have [Fe/H] < ∼ −3 and three stars are below [Fe/H] ∼ −3.5. This constitutes the first evidence that the classical dSphs Fornax and Sextans join Sculptor in containing extremely metal-poor stars and suggests that all of the classical dSphs contain extremely metal-poor stars. One giant in Sculptor at [Fe/H] = −3.96 ± 0.06 is the most metal-poor star ever observed in an external galaxy. We carried out a detailed analysis of the chemical abundances of the α, iron peak, and the heavy elements, and we performed a comparison with the Milky Way halo and the ultra faint dwarf stellar populations. Carbon, barium, and strontium show distinct features characterized by the early stages of galaxy formation and can constrain the origin of their nucleosynthesis.

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Section: Discussionmentioning

confidence: 99%

Extremely metal-poor stars in classical dwarf spheroidal galaxies: Fornax, Sculptor, and Sextans

Tafelmeyer

Jablonka

Hill

et al. 2010

A&A

152

287

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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. The dominant isotope of Fe, 56 Fe (91.7% of the solar Fe abundance), is produced as radioactive 56 Ni at very high temperatures, T > 4 × 10 9 K .…”

Section: Nucleosynthesismentioning

confidence: 99%

“…The amount of Fe-peak elements ejected in a SN II primarily depends on the explosion energy and the mass cut between the ejected material and the collapsed core (note that these parameters are related, although they are often treated independently, e.g., Umeda & Nomoto 2002). Less Cr is produced relative to Fe for a deeper mass cut (Nakamura et al 1999;Umeda & Nomoto 2002). Current estimates of the mass cut are based on the mass ejected in the form of 56 Ni and the ratio 58 Ni/ 56 Ni, which are determined from SN II light curves and spectra.…”

Section: Nucleosynthesismentioning

confidence: 99%

“…Current estimates of the mass cut are based on the mass ejected in the form of 56 Ni and the ratio 58 Ni/ 56 Ni, which are determined from SN II light curves and spectra. Other parameters affecting the relative production of Fe-group nuclei, include the degree of mixing and fallback to the remnant, and both the energy and geometry of the explosion (Nakamura et al 1999;Umeda & Nomoto 2002, 2005. Nagataki et al (1997) demonstrated that an axisymmetric explosion in SN II models enhances the production of 52 Cr.…”

Section: Nucleosynthesismentioning

confidence: 99%

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

Bergemann

Cescutti

2010

A&A

164

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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“…The core-collapse SN II yields are adopted from WW95. However, for lower metallicities, we use the results of highexplosion-energy hypernovae (Umeda & Nomoto 2002Nomoto et al 2006Nomoto et al , 2013 because the latter models reproduce the large [Zn/Fe] ratios of halo stars and lowmetallicity Damped Lyman-α systems (see Barbuy et al 2015). At near-solar metallicities, the Zn underproduction problem (e.g.…”

Section: Introductionmentioning

confidence: 99%

Tracing the evolution of the Galactic bulge with chemodynamical modelling of alpha-elements

Friaça

Barbuy

2017

A&A

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Context. Galactic bulge abundances can be best understood as indicators of bulge formation and nucleosynthesis processes by comparing them with chemo-dynamical evolution models. Aims. The aim of this work is to study the abundances of alpha-elements in the Galactic bulge, including a revision of the oxygen abundance in a sample of 56 bulge red giants. Methods. Literature abundances for O, Mg, Si, Ca and Ti in Galactic bulge stars are compared with chemical evolution models. For oxygen in particular, we reanalysed high-resolution spectra obtained using FLAMES+UVES on the Very Large Telescope, now taking each star's carbon abundances, derived from CI and C 2 lines, into account simultaneously.Results. We present a chemical evolution model of alpha-element enrichment in a massive spheroid that represents a typical classical bulge evolution. The code includes multi-zone chemical evolution coupled with hydrodynamics of the gas. Comparisons between the model predictions and the abundance data suggest a typical bulge formation timescale of 1-2 Gyr. The main constraint on the bulge evolution is provided by the O data from analyses that have taken the C abundance and dissociative equilibrium into account. Mg, Si, Ca and Ti trends are well reproduced, whereas the level of overabundance critically depends on the adopted nucleosynthesis prescriptions.

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Nucleosynthesis of Zinc and Iron Peak Elements in Population III Type II Supernovae: Comparison with Abundances of Very Metal Poor Halo Stars

Cited by 540 publications

References 66 publications

Extremely metal-poor stars in classical dwarf spheroidal galaxies: Fornax, Sculptor, and Sextans

Extremely metal-poor stars in classical dwarf spheroidal galaxies: Fornax, Sculptor, and Sextans

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

Tracing the evolution of the Galactic bulge with chemodynamical modelling of alpha-elements

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