THE IMPACT OF UPDATED Zr NEUTRON-CAPTURE CROSS SECTIONS AND NEW ASYMPTOTIC GIANT BRANCH MODELS ON OUR UNDERSTANDING OF THE<i>S</i>PROCESS AND THE ORIGIN OF STARDUST

Lugaro, Maria; Tagliente, G.; Karakas, Amanda I.; Milazzo, Paolo; Käppeler, F.; Davis, A. M.; Savina, M. R.

doi:10.1088/0004-637x/780/1/95

Cited by 61 publications

(90 citation statements)

References 90 publications

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“…We also hope to have found a specific physical mechanism suitable to account for the constraints from presolar SiC grains, because our fits are in general of a quality at least comparable to the best ones discussed in Liu et al (2014a), Liu et al (2014b), Liu et al (2015) and Lugaro et al (2014).…”

Section: Discussionmentioning

confidence: 70%

“…They were made using exploratory descriptions for the 13 C pocket, as outlined in the previous sections (see also, e.g., Liu et al, 2014a;Liu et al, 2014b;Lugaro et al, 2014 could not be reproduced (see Figs. 5 and 7 in that paper).…”

Section: Discussionmentioning

confidence: 99%

“…For them we followed the suggestion by Liu et al (2014a) that the decay of 135 Cs (t 1=2 ¼ 2 Ma) had no time to occur before dust formation in the circumstellar envelope and must therefore be excluded in computing the 135 Ba/ 136 Ba ratio of SiC grains. In general, we account for the measurements of Ba isotopes at the same level of accuracy previously possible, considering together the results by Lugaro et al (2014) and the whole set of different attempots by Liu et al (2014a). However, some data points still remain outside the reach od AGB modelling.…”

Section: Discussionmentioning

confidence: 99%

“…These last scenarios intentionally avoid a reference to a physical mechanism, in order to offer general guidelines to subsequent models: see e.g. the clear discussions made by Liu et al (2015) and Lugaro et al (2014). This is the fundamental difference between our procedure and those previous works.…”

Section: àðKþ1þmentioning

confidence: 99%

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s-Processing from MHD-induced mixing and isotopic abundances in presolar SiC grains

Palmerini

Trippella

Busso

et al. 2018

Geochimica et Cosmochimica Acta

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In the past years the observational evidence that s-process elements from Sr to Pb are produced by stars ascending the socalled Asymptotic Giant Branch (or ''AGB") could not be explained by self-consistent models, forcing researchers to extensive parameterizations. The crucial point is to understand how protons can be injected from the envelope into the He-rich layers, yielding the formation of 13 C and then the activation of the 13 Cða; nÞ 16 O reaction. Only recently, attempts to solve this problem started to consider quantitatively physically-based mixing mechanisms. Among them, MHD processes in the plasma were suggested to yield mass transport through magnetic buoyancy. In this framework, we compare results of nucleosynthesis models for Low Mass AGB Stars (M K 3M ), developed from the MHD scenario, with the record of isotopic abundance ratios of s-elements in presolar SiC grains, which were shown to offer precise constraints on the 13 C reservoir. We find that n-captures driven by magnetically-induced mixing can indeed account for the SiC data quite well and that this is due to the fact that our 13 C distribution fulfils the above constraints rather accurately. We suggest that similar tests should be now performed using different physical models for mixing. Such comparisons would indeed improve decisively our understanding of the formation of the neutron source.

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Section: Discussionmentioning

confidence: 70%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: àðKþ1þmentioning

confidence: 99%

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s-Processing from MHD-induced mixing and isotopic abundances in presolar SiC grains

Palmerini

Trippella

Busso

et al. 2018

Geochimica et Cosmochimica Acta

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“…In this case the 13 C pocket is artificially included as in the other models, however, because the temperature in that region only reaches up to 70 MK before the onset of the following thermal instability, the 13 C(α,n) 16 O reaction is not activated until the 13 C nuclei are ingested in the following convective region [58]. In this case the impact of the 14 N(n,p) 14 C neutron poison reaction is even more crucial because the large amount of 14 N present in the H-burning ashes is ingested at the same time.…”

Section: Impact For S-process Calculationsmentioning

confidence: 99%

Accelerator mass spectrometry measurements of theC13(n,γ)C14and
Wallner
¹
,
Bichler
²
,
Buczak
³

et al. 2016
Phys. Rev. C
28
1
17
0
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The technique of accelerator mass spectrometry (AMS), offering a complementary tool for sensitive studies of key reactions in nuclear astrophysics, was applied for measurements of the 13 C(n,γ ) 14 C and the 14 N(n,p) 14 C cross sections, which act as a neutron poison in s-process nucleosynthesis. Solid samples were irradiated at Karlsruhe Institute of Technology with neutrons closely resembling a Maxwell-Boltzmann distribution for kT = 25 keV, and also at higher energies between E n = 123 and 182 keV. After neutron irradiation the produced amount of 14 C in the samples was measured by AMS at the Vienna Environmental Research Accelerator (VERA) facility. For both reactions the present results provide important improvements compared to previous experimental data, which were strongly discordant in the astrophysically relevant energy range and missing for the comparably strong resonances above 100 keV. For 13 C(n,γ ) we find a four times smaller cross section around kT = 25 keV than a previous measurement. For 14 N(n,p), the present data suggest two times lower cross sections between 100 and 200 keV than had been obtained in previous experiments and data evaluations. The effect of the new stellar cross sections on the s process in low-mass asymptotic giant branch stars was studied for stellar models of 2 M initial mass, and solar and 1/10 th solar metallicity.

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Indirect $$(n, \gamma )^{91,92}$$ Zr Cross Section Measurements for the s-Process

Guttormsen

Goriely

Larsen

et al. 2019

Springer Proceedings in Physics

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Nuclear level densities (NLDs) and γ-ray strength functions (γ SFs) have been extracted from particle-γ coincidences of the 92 Zr(p,p γ) 92 Zr and 92 Zr(p,dγ) 91 Zr reactions using the Oslo method. The new 91,92 Zr γ SF data, combined with photonuclear cross sections, cover the whole energy range from E γ ≈ 1.5 MeV up to the giant dipole resonance at E γ ≈ 17 MeV. The wide-range γ SF data display structures at E γ ≈ 9.5 MeV, compatible with a superposition of the spin-flip M1 resonance and a pygmy E1 resonance. Furthermore, the γ SF shows a minimum at E γ ≈ 2-3 MeV and an increase at lower γ-ray energies. The experimentally constrained NLDs and γ SFs are shown to reproduce known (n,γ) and Maxwellian-averaged cross sections for 91,92 Zr using the TALYS reaction code, thus serving as a benchmark for this indirect method of estimating (n,γ) cross sections for Zr isotopes.

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THE IMPACT OF UPDATED Zr NEUTRON-CAPTURE CROSS SECTIONS AND NEW ASYMPTOTIC GIANT BRANCH MODELS ON OUR UNDERSTANDING OF THESPROCESS AND THE ORIGIN OF STARDUST

Cited by 61 publications

References 90 publications

s-Processing from MHD-induced mixing and isotopic abundances in presolar SiC grains

s-Processing from MHD-induced mixing and isotopic abundances in presolar SiC grains

Accelerator mass spectrometry measurements of theC13(n,γ)C14and
Wallner
¹
,
Bichler
²
,
Buczak
³

et al. 2016
Phys. Rev. C
28
1
17
0
View full text Add to dashboard Cite

Indirect $$(n, \gamma )^{91,92}$$ Zr Cross Section Measurements for the s-Process

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THE IMPACT OF UPDATED Zr NEUTRON-CAPTURE CROSS SECTIONS AND NEW ASYMPTOTIC GIANT BRANCH MODELS ON OUR UNDERSTANDING OF THESPROCESS AND THE ORIGIN OF STARDUST

Cited by 61 publications

References 90 publications

s-Processing from MHD-induced mixing and isotopic abundances in presolar SiC grains

s-Processing from MHD-induced mixing and isotopic abundances in presolar SiC grains

Accelerator mass spectrometry measurements of theC13(n,γ)C14andWallner1, Bichler2, Buczak3 et al. 2016Phys. Rev. C281170View full textAdd to dashboardCite

Indirect $$(n, \gamma )^{91,92}$$ Zr Cross Section Measurements for the s-Process

Contact Info

Product

Resources

About

Accelerator mass spectrometry measurements of theC13(n,γ)C14and
Wallner
¹
,
Bichler
²
,
Buczak
³

et al. 2016
Phys. Rev. C
28
1
17
0
View full text Add to dashboard Cite