RUBIDIUM ABUNDANCES IN THE GLOBULAR CLUSTERS NGC 6752, NGC 1904, AND NGC 104 (47 Tuc)

D’Orazi, V.; Lugaro, Maria; Campbell, Simon; Bragaglia, A.; Carretta, E.; Gratton, R.; Lucatello, S.; D’Antona, F.

doi:10.1088/0004-637x/776/1/59

Cited by 20 publications

(9 citation statements)

References 78 publications

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“…Because of the high peak neutron density (N n ∼ 10 12 n cm −3 ), 86 Kr, 87 Rb, and 96 Zr are strongly overproduced, owing to the branchings at 85 Kr, 86 Rb, and 95 Zr. The observational evidence of the strong activation of the 22 Ne(α, n) 25 Mg reaction (associated to IMS) is the excess of Rb with respect to Zr (see, e.g., Lambert et al 1995;Tomkin & Lambert 1999;Abia et al 2001, and most recently Yong et al 2008;García-Hernández et al 2009D'Orazi et al 2013). The high [Rb/Zr] observed in some OH/IR AGB stars seems to be incompatible with IMS predictions.…”

Section: The Agb Yieldsmentioning

confidence: 99%

GALACTIC CHEMICAL EVOLUTION AND SOLARs-PROCESS ABUNDANCES: DEPENDENCE ON THE¹³C-POCKET STRUCTURE

Bisterzo

Travaglio²,

Gallino

et al. 2014

ApJ

274

465

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We study the s-process abundances (A 90) at the epoch of the solar system formation. Asymptotic giant branch yields are computed with an updated neutron capture network and updated initial solar abundances. We confirm our previous results obtained with a Galactic chemical evolution (GCE) model: (1) as suggested by the s-process spread observed in disk stars and in presolar meteoritic SiC grains, a weighted average of s-process strengths is needed to reproduce the solar s distribution of isotopes with A > 130; and (2) an additional contribution (of about 25%) is required in order to represent the solar s-process abundances of isotopes from A = 90 to 130. Furthermore, we investigate the effect of different internal structures of the 13 C pocket, which may affect the efficiency of the 13 C(α, n)16 O reaction, the major neutron source of the s process. First, keeping the same 13 C profile adopted so far, we modify by a factor of two the mass involved in the pocket; second, we assume a flat 13 C profile in the pocket, and we test again the effects of the variation of the mass of the pocket. We find that GCE s predictions at the epoch of the solar system formation marginally depend on the size and shape of the 13 C pocket once a different weighted range of 13 C-pocket strengths is assumed. We obtain that, independently of the internal structure of the 13 C pocket, the missing solar system s-process contribution in the range from A = 90 to 130 remains essentially the same.

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Section: The Agb Yieldsmentioning

confidence: 99%

GALACTIC CHEMICAL EVOLUTION AND SOLARs-PROCESS ABUNDANCES: DEPENDENCE ON THE¹³C-POCKET STRUCTURE

Bisterzo

Travaglio²,

Gallino

et al. 2014

ApJ

274

465

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“…In the present work we again provide our predictions for Ba and Sr but also include two other light neutron-capture elements that have not been modelled before, Zr and Rb. In particular, Rb has only been measured in a few globular clusters (Barbuy et al 2014;Yong et al 2008Yong et al , 2014D'Orazi et al 2013;Wallerstein et al 2007). …”

Section: Introductionmentioning

confidence: 99%

The role of neutron star mergers in the chemical evolution of the Galactic halo

Cescutti

Romano

Matteuccí

et al. 2015

A&A

144

214

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Context. The dominant astrophysical production site of the r-process elements has not yet been unambiguously identified. The suggested main r-process sites are core-collapse supernovae and merging neutron stars. Aims. We explore the problem of the production site of Eu. We also use the information present in the observed spread in the Eu abundances in the early Galaxy, and not only its average trend. Moreover, we extend our investigations to other heavy elements (Ba, Sr, Rb, Zr) to provide additional constraints on our results. Methods. We adopt a stochastic chemical evolution model that takes inhomogeneous mixing into account. The adopted yields of Eu from merging neutron stars and from core-collapse supernovae are those that are able to explain the average [Eu/Fe]-[Fe/H] trend observed for solar neighbourhood stars, the solar abundance of Eu, and the present-day abundance gradient of Eu along the Galactic disc in the framework of a well-tested homogeneous model for the chemical evolution of the Milky Way. Rb, Sr, Zr, and Ba are produced by both the s-and r-processes. The r-process yields were obtained by scaling the Eu yields described above according to the abundance ratios observed in r-process rich stars. The s-process contribution by spinstars is the same as in our previous papers. Results. Neutron star binaries that merge in less than 10 Myr or neutron star mergers combined with a source of r-process generated by massive stars can explain the spread of [Eu/Fe] in the Galactic halo. The combination of r-process production by neutron star mergers and s-process production by spinstars is able to reproduce the available observational data for Sr, Zr, and Ba. We also show the first predictions for Rb in the Galactic halo. Conclusions. We confirm previous results that either neutron star mergers on a very short timescale or both neutron star mergers and at least a fraction of Type II supernovae have contributed to the synthesis of Eu in the Galaxy. The r-process production of Sr, Zr, and Ba by neutron star mergers -complemented by an s-process production by spinstars -provide results that are compatible with our previous findings based on other r-process sites. We critically discuss the weak and strong points of both neutron star merging and supernova scenarios for producing Eu and eventually suggest that the best solution is probably a mixed one in which both sources produce Eu. In fact, this scenario reproduces the scatter observed in all the studied elements better.

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“…Due to their low abundance and low ionization potential, K and Rb have only a small number of lines observable in the visual and infrared spectrum, due to the neutral species, and these features are often blended. However, recent years have seen an increase in interest in these elements, particularly in globular cluster stars, due to discovered anticorrelations of K with Mg abundances (Cohen & Kirby 2012;Mucciarelli et al 2012Mucciarelli et al , 2015Iliadis et al 2016;Mucciarelli, Merle & Bellazzini 2017), and the use of Rb as an important diagnostic of the nature of the s-process (Yong et al 2006;D'Orazi1 et al 2013;Yong et al 2014). Numerous statistical equilibrium calculations have been performed for K (Shchukina 1987;Bruls, Rutten & Shchukina 1992;Takeda et al 1996;Ivanova & Shimanskiȋ 2000;Takeda et al 2002;Zhang et al 2006a,b;Scott et al 2015), often with hydrogen collisions included using a scaling of the Drawin formula (Steenbock & Holweger 1984).…”

Section: Introductionmentioning

confidence: 99%

Data on inelastic processes in low-energy potassium-hydrogen and rubidium-hydrogen collisions

Yakovleva

Barklem

Belyaev

2017

Monthly Notices of the Royal Astronomical Society

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Two sets of rate coefficients for low-energy inelastic potassium-hydrogen and rubidiumhydrogen collisions were computed for each collisional system based on two model electronic structure calculations, performed by the quantum asymptotic semi-empirical and the quantum asymptotic linear combinations of atomic orbitals (LCAO) approaches, followed by quantum multichannel calculations for the non-adiabatic nuclear dynamics. The rate coefficients for the charge transfer (mutual neutralization, ion-pair formation), excitation and de-excitation processes are calculated for all transitions between the five lowest lying covalent states and the ionic states for each collisional system for the temperature range 1000-10 000 K. The processes involving higher lying states have extremely low rate coefficients and, hence, are neglected. The two model calculations both single out the same partial processes as having large and moderate rate coefficients. The largest rate coefficients correspond to the mutual neutralization processes into the K(5s 2 S) and Rb(4d 2 D) final states and at temperature 6000 K have values exceeding 3 × 10 −8 cm 3 s −1 and 4 × 10 −8 cm 3 s −1 , respectively. It is shown that both the semi-empirical and the LCAO approaches perform equally well on average and that both sets of atomic data have roughly the same accuracy. The processes with large and moderate rate coefficients are likely to be important for non-LTE modelling in atmospheres of F, G and K-stars, especially metal-poor stars.

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RUBIDIUM ABUNDANCES IN THE GLOBULAR CLUSTERS NGC 6752, NGC 1904, AND NGC 104 (47 Tuc)

Cited by 20 publications

References 78 publications

GALACTIC CHEMICAL EVOLUTION AND SOLARs-PROCESS ABUNDANCES: DEPENDENCE ON THE¹³C-POCKET STRUCTURE

GALACTIC CHEMICAL EVOLUTION AND SOLARs-PROCESS ABUNDANCES: DEPENDENCE ON THE¹³C-POCKET STRUCTURE

The role of neutron star mergers in the chemical evolution of the Galactic halo

Data on inelastic processes in low-energy potassium-hydrogen and rubidium-hydrogen collisions

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RUBIDIUM ABUNDANCES IN THE GLOBULAR CLUSTERS NGC 6752, NGC 1904, AND NGC 104 (47 Tuc)

Cited by 20 publications

References 78 publications

GALACTIC CHEMICAL EVOLUTION AND SOLARs-PROCESS ABUNDANCES: DEPENDENCE ON THE13C-POCKET STRUCTURE

GALACTIC CHEMICAL EVOLUTION AND SOLARs-PROCESS ABUNDANCES: DEPENDENCE ON THE13C-POCKET STRUCTURE

The role of neutron star mergers in the chemical evolution of the Galactic halo

Data on inelastic processes in low-energy potassium-hydrogen and rubidium-hydrogen collisions

Contact Info

Product

Resources

About

GALACTIC CHEMICAL EVOLUTION AND SOLARs-PROCESS ABUNDANCES: DEPENDENCE ON THE¹³C-POCKET STRUCTURE

GALACTIC CHEMICAL EVOLUTION AND SOLARs-PROCESS ABUNDANCES: DEPENDENCE ON THE¹³C-POCKET STRUCTURE