Neutron capture cross sections for the weak<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>s</mml:mi></mml:mrow></mml:math>process in massive stars

Heil, M.; Käppeler, F.; Uberseder, E.; Gallino, R.; Pignatari, M.

doi:10.1103/physrevc.77.015808

Cited by 74 publications

(88 citation statements)

References 30 publications

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“…Maxwellian averaged cross section (b) TOF technique Activation method 58 Fe 12.1±1.1 (Käppeler et al, 1983) 13.5±0.7 (Heil et al, 2008c) 59 Co 38±3 (Spencer and Macklin, 1976) 39.6±2.7 (Heil et al, 2008c) (Koehler et al, 2000 6.13±0.18 (Käppeler et al, 1990b) Musgrove et al, 1978) 19.0±0.6 (Käppeler et al, 1990b) Bao et al (2000). …”

Section: Target Isotopementioning

confidence: 99%

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Thesprocess: Nuclear physics, stellar models, and observations

et al. 2011

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Nucleosynthesis in the s process takes place in the He burning layers of low mass AGB stars and during the He and C burning phases of massive stars. The s process contributes about half of the element abundances between Cu and Bi in solar system material. Depending on stellar mass and metallicity the resulting s-abundance patterns exhibit characteristic features, which provide comprehensive information for our understanding of the stellar life cycle and for the chemical evolution of galaxies. The rapidly growing body of detailed abundance observations, in particular for AGB and post-AGB stars, for objects in binary systems, and for the very faint metal-poor population represents exciting challenges and constraints for stellar model calculations. Based on updated and improved nuclear physics data for the s-process reaction network, current models are aiming at ab initio solution for the stellar physics related to convection and mixing processes. Progress in the intimately related areas of observations, nuclear and atomic physics, and stellar modeling is reviewed and the corresponding interplay is illustrated by the general abundance patterns of the elements beyond iron and by the effect of sensitive branching points along the sprocess path. The strong variations of the s-process efficiency with metallicity bear also interesting consequences for Galactic chemical evolution.

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Section: Target Isotopementioning

confidence: 99%

“…Correspondingly, calculated cross sections are needed to extrapolate the results from activation measurements to the entire temperature range of the various s-process sites (see Ref. (Heil et al, 2008c)). …”

Section: Maxwellian Averaged Cross Sectionsmentioning

confidence: 99%

Thesprocess: Nuclear physics, stellar models, and observations

et al. 2011

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“…This nucleus has a magic number of neutrons of 50 and a low Maxwellian-averaged neutron capture cross-section of 15.7 mbarn at a thermal energy of 30 keV, as compared to 234 for 85 Rb (Heil et al 2008). This means that if 87 Rb is produced, it tends to accumulate.…”

Section: Introductionmentioning

confidence: 99%

Rubidium, zirconium, and lithium production in intermediate-mass asymptotic giant branch stars

Raai¹,

Lugaro

Karakas

et al. 2012

A&A

120

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Context.A recent survey of a large sample of Galactic intermediate-mass (>3 M ) asymptotic giant branch (AGB) stars shows that they exhibit large overabundances of rubidium (Rb) up to 100-1000 times solar. In contrast, zirconium (Zr) is not enriched in these stars compared to its solar abundances. These observations set constraints on our theoretical notion of the slow neutron capture process (s process) that occurs inside intermediate-mass AGB stars. Lithium (Li) abundances are also reported for these stars. In intermediate-mass AGB stars, Li can be produced by proton captures occuring at the base of the convective envelope. For this reason the observations of Rb, Zr, and Li set complementary constraints on different processes occurring in the same stars. Aims. We present predictions for the abundances of Rb, Zr, and Li as computed for the first time simultaneously in intermediate-mass AGB star models and compare them to the current observational constraints. Methods. We calculate the Rb, Zr, and Li surface abundances for stellar models with masses between 3 and 6.5 M and metallicities between 0.02 and 0.004. Results. We find that the Rb abundance increases with increasing stellar mass, as is inferred from observations but we are unable to match the highest observed [Rb/Fe] abundances. Variations of the reaction rates of the neutron-capture cross sections involved with Rb production and the rate of the 22 Ne(α, n) 25 Mg reaction, responsible for neutron production inside these stars, yield only modest variations in the surface Rb content of ≈0.3 dex. Inclusion of a partial mixing zone (PMZ) to activate the 13 C(α, n) 16 O reaction as an additional neutron source yields significant enhancements in the Rb abundance. However this leads to Zr abundances that exceed the upper limits of the current observational constraints. If the third dredge-up (TDU) efficiency remains as high during the final stages of AGB evolution as during the earlier stages, we can match the lowest values of the observed Rb abundance range. We predict large variations in the Li abundance, which are observed. Finally, the predicted Rb production increases with decreasing metallicity, in qualitative agreement with observations of Magellanic Cloud AGB stars. However stellar models of Z = 0.008 and Z = 0.004 intermediate-mass AGB stars do not produce enough Rb to match the observed abundances.

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“…For a reliable description of the propagation effect, a number of MACS uncertainties remain to be resolved by new accurate cross section measurements. In addition to the light neutron poisons, this concerns especially the MACS values of less than 100 mbarn for the isotopes along the s-process path between Fe and Sr [7,[48][49][50][51].…”

Section: Massive Starsmentioning

confidence: 99%

Erratum: Stellar neutron capture cross sections ofNe20,21,22[Phys. Rev. C90, 045804 (2014)]

Heil¹,

Plag²,

Uberseder³

et al. 2015

Phys. Rev. C

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The stellar (n,γ ) cross sections of the Ne isotopes are important for a number of astrophysical quests, i.e., for the interpretation of abundance patterns in presolar material or with respect to the s-process neutron balance in red giant stars. This paper presents resonance studies of experimental data in the keV range, which had not been fully analyzed before. The analyses were carried out with the R-matrix code SAMMY. With these results for the resonant part and by adding the components due to direct radiative capture, improved Maxwellian-averaged cross sections (MACS) could be determined. At kT = 30 keV thermal energy we obtain MACS values of 240 ± 29, 1263 ± 160, and 53.2 ± 2.7 μbarn for

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Neutron capture cross sections for the weaksprocess in massive stars

Cited by 74 publications

References 30 publications

Thesprocess: Nuclear physics, stellar models, and observations

Thesprocess: Nuclear physics, stellar models, and observations

Rubidium, zirconium, and lithium production in intermediate-mass asymptotic giant branch stars

Erratum: Stellar neutron capture cross sections ofNe20,21,22[Phys. Rev. C90, 045804 (2014)]

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