Measurement of the Rb-85 and Rb-87 capture cross sections for s-process studies

Beer, H.; Macklin, R. L.

doi:10.1086/167351

Cited by 73 publications

(51 citation statements)

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“…For example, the amount of Rb produced during the s-process depends on the probability of the two unstable nuclei 85 Kr and 86 Rb capturing a neutron before decaying. These two isotopes therefore act as 'branching points' and the probability of this occurring depends on the local neutron density (Beer & Macklin 1989 Sr (or Y or Zr). In constrast, during the operation of the 13 C neutron source these branching points are not efficiently activated and the ratio of Rb to Sr (or Y or Zr) remains less than unity.…”

Section: Karakas and Lattanziomentioning

confidence: 99%

The Dawes Review 2: Nucleosynthesis and Stellar Yields of Low- and Intermediate-Mass Single Stars

Karakas

Lattanzio

2014

Publ. Astron. Soc. Aust.

650

675

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The chemical evolution of the Universe is governed by the chemical yields from stars, which in turn are determined primarily by the initial stellar mass. Even stars as low as 0.9 M can, at low metallicity, contribute to the chemical evolution of elements. Stars less massive than about 10 M experience recurrent mixing events that can significantly change the surface composition of the envelope, with observed enrichments in carbon, nitrogen, fluorine, and heavy elements synthesized by the slow neutron capture process (the s-process). Low-and intermediate-mass stars release their nucleosynthesis products through stellar outflows or winds, in contrast to massive stars that explode as core-collapse supernovae. Here we review the stellar evolution and nucleosynthesis for single stars up to ∼10 M from the main sequence through to the tip of the asymptotic giant branch (AGB). We include a discussion of the main uncertainties that affect theoretical calculations and review the latest observational data, which are used to constrain uncertain details of the stellar models. We finish with a review of the stellar yields available for stars less massive than about 10 M and discuss efforts by various groups to address these issues and provide homogeneous yields for low-and intermediate-mass stars covering a broad range of metallicities. Keywords

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Section: Karakas and Lattanziomentioning

confidence: 99%

The Dawes Review 2: Nucleosynthesis and Stellar Yields of Low- and Intermediate-Mass Single Stars

Karakas

Lattanzio

2014

Publ. Astron. Soc. Aust.

650

675

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“…Experimental cross sections for 85 Rb is taken from Ref. [49]. The neutron magic isotope 87 Rb also acts as an important bottleneck to the s-process reaction flow.…”

Section: B Total Capture Cross Sectionsmentioning

confidence: 99%

Neutron capture reactions relevant to thesandpprocesses in the region of theN=50shell closure

2016

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Radiative thermal neutron capture cross sections for nuclei participating in s-process and pprocess nucleosynthesis in and around N = 50 closed neutron shell have been calculated in statistical semi-microscopic Hauser-Feshbach approach for the energy range of astrophysical interest. A folded optical-model potential is constructed utilizing the standard DDM3Y real nucleon-nucleon interaction. The folding of the interaction with target radial matter densities, obtained from the relativistic-mean-field approach, is done in coordinate space using the spherical approximation. The standard nuclear reaction code TALYS1.8 is used for cross-section calculation. The cross sections are compared with experimental results and reasonable agreements are found for almost all cases. Maxwellian-averaged cross sections (MACS) for the nuclei are presented at a single thermal energy of 30 keV relevant to s-process. We have also presented the MACS values over a range of energy from 5 to 100 keV for neutron magic nuclei with (N = 50).PACS numbers: I. INTRODUCTIONElements heavier than iron are produced via two principle processes, namely, the slow neutron capture process (s-process) and the rapid neutron capture process (r-process), differing in the respective neutron capture timescales with respect to the β-decay half-lives. There is a minor contribution from another process, namely, pprocess, producing a subset of proton-rich isotopes. The detailed study of the heavy element nucleosynthesis was done in the fundamental work of Burbidge et al. [1] and also of Cameron [2]. Recently Käppeler et al. [3] presented a review of progress on the studies of s-process nucleosynthesis with advanced nuclear physics inputs, observational data, and stellar models.While the majority of the theory of the s-process is well-developed, uncertainty still remains in constraining the neutron capture rates of nuclei involved in nucleosynthesis chain. The capture cross sections are highly scattered and uncertain in the energy range appropriate for astrophysical applications. These uncertainties lead to significant errors in determining exact abundances of elements involved in different processes. Many works * Electronic address: saumidutta89@gmail.com † Electronic address: ggphy@caluniv.ac.in ‡ Electronic address: abhattacharyyacu@gmail.com have been devoted to this respect in order to measure the thermal neutron capture cross sections relevant to s-process temperature. However, reactions on some important nuclei are still not available due to their unavailability in the terrestrial laboratory. Käppeler et al. [4] showed the present status of the uncertainty of stellar (n, γ) cross sections and commented that improvements are certainly necessary especially in the mass region below A=120 and above A=180. Some reactions are of significant importance, basically those with closed neutron shells acting as bottlenecks to the s-process reaction flow. They have very low cross-sections and in some scenarios, the s-process reaction flow cannot overcome these bottlen...

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“…The relative abundances of s-elements that follow the 85 Kr reaction branching (Rb, Sr, Zr and Y) along the s-process path yield information on the neutron density prevailing during the neutron capture processes occurring in the He intershell (Beer & Macklin 1989;Lambert et al 1995;Abia et al 2001). In particular, the [Rb/Sr] helps to discriminate between the two main neutron sources, the 13 C(α, n) 16 O and 22 Ne(α, n) 25 Mg, operating in TP-AGB stars.…”

Section: Heavy Elementsmentioning

confidence: 99%

Chemical analysis of carbon stars in the Local Group

Laverny¹,

Abia

Domínguez

et al. 2006

A&A

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We present the first results of our ongoing chemical study of carbon stars in the Local Group of galaxies. We used spectra obtained with UVES at the 8.2 m Kueyen-VLT telescope and a new grid of spherical model atmospheres for cool carbon-rich stars which include polyatomic opacities, to perform a full chemical analysis of one carbon star, BMB-B 30, in the Small Magellanic Cloud (SMC) and two, IGI95-C1 and IGI95-C3, in the Sagittarius Dwarf Spheroidal (Sgr dSph) galaxy. Our main goal is to test the dependence on the stellar metallicity of the s-process nucleosynthesis and mixing mechanism occurring in AGB stars. For these three stars, we find important s-element enhancements with respect to the mean metallicity ([M/H]), namely [s/M] ≈ +1.0, similar to the figure found in galactic AGB stars of similar metallicity. The abundance ratios derived between elements belonging to the first and second s-process abundance peaks, corresponding to nuclei with a magic number of neutrons N = 50 (88Sr, 89Y, 90Zr) and N = 82 (138Ba, 139La, 140Ce, 141Pr), agree remarkably well with the theoretical predictions of low mass (M < 3 M ) metal-poor AGB nucleosynthesis models where the main source of neutrons is the 13 C(α, n) 16 O reaction activated during the long interpulse phase, in a small pocket located within the He-rich intershell. The derived C/O and 12 C/ 13 C ratios are, however, more difficult to reconcile with theoretical expectations. Possible explanations, like the extrinsic origin of the composition of these carbon stars or the operation of a non-standard mixing process during the AGB phase (such as the cool bottom process), are discussed on the basis of the collected observational constraints.

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Measurement of the Rb-85 and Rb-87 capture cross sections for s-process studies

Cited by 73 publications

References 0 publications

The Dawes Review 2: Nucleosynthesis and Stellar Yields of Low- and Intermediate-Mass Single Stars

The Dawes Review 2: Nucleosynthesis and Stellar Yields of Low- and Intermediate-Mass Single Stars

Neutron capture reactions relevant to thesandpprocesses in the region of theN=50shell closure

Chemical analysis of carbon stars in the Local Group

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