The Origin of r-process Elements in the Milky Way

Côté, Benoît; Fryer, Chris L.; Belczyński, Krzysztof; Korobkin, Oleg; Chruślińska, Martyna; Vassh, Nicole; Mumpower, Matthew; Lippuner, Jonas; Sprouse, Trevor; Surman, Rebecca; Wollaeger, Ryan

doi:10.3847/1538-4357/aaad67

Cited by 226 publications

(203 citation statements)

References 124 publications

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“…Uncertainties for  96 Mo and  100 Ru are given as the 2 standard error of the mean and the 95% confidence interval, respectively. process is believed to occur in core-collapse supernovae 27 , while the r-process most likely occurs in neutron star mergers 28,29 , two distinct stellar environments. A small enrichment of supernovae derived material in the outer Solar System was proposed to account for the isotope dichotomy between carbonaceous (CC) and non-carbonaceous meteorites (NC) [30][31][32] .…”

Section: Mixing Interstellar Medium Grown Dust With Stardustmentioning

confidence: 99%

The origin of s-process isotope heterogeneity in the solar protoplanetary disk

Hunt

Lugaro

et al. 2019

Nat Astron

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Rocky asteroids and planets display nucleosynthetic isotope variations that are attributed to the heterogeneous distribution of stardust from different stellar sources in the solar protoplanetary disk. Here we report new high precision palladium isotope data for six iron meteorite groups, which display smaller nucleosynthetic isotope variations than the more refractory neighbouring elements. Based on this observation we present a new model in which thermal destruction of interstellar medium dust results in an enrichment of s-process dominated stardust in regions closer to the Sun. We propose that stardust is depleted in volatile elements due to incomplete condensation of these elements into dust around asymptotic giant branch (AGB) stars. This led to the smaller nucleosynthetic variations for Pd reported here and the lack of such variations for more volatile elements. The smaller magnitude variations measured in heavier refractory elements suggest that material from high-metallicity AGB stars dominated stardust in the Solar System. These stars produce less heavy s-process elements (Z ≥ 56) compared to the bulk Solar System composition.The protoplanetary disk from which our Solar System formed incorporated dust that was inherited from the collapsing molecular cloud. A few per cent of this dust formed around stars with active nucleosynthesis and retained the extreme isotopic fingerprint of its formation environment 1,2 . This dust, which is isotopically anomalous compared to Solar System compositions, is here termed stardust. However, it is often also referred to as presolar grains when found in meteorites. Most stardust in primitive meteorites originates from asymptotic giant branch (AGB) stars, the site of s-process nucleosynthesis, with only small contributions from supernovae environments 3 . The majority of the dust in the solar protoplanetary disk grew in the interstellar medium (ISM) from a well-mixed gas phase as mantles on pre-existing nuclei. These mantles likely inherited the composition of the local ISM, i.e., a near solar isotopic composition 1 .Nucleosynthetic isotope variations, relative to Earth, are well established for a range of elements in bulk meteorites 4 . These variations mostly reflect the heterogeneous distribution of isotopically distinct dust in the protoplanetary disk. It is generally thought that this heterogeneity was established, at least in part, due to processes occurring in the protoplanetary disk itself. Physical sorting of grains, either by mineralogical type 5 or size 6 , and selective destruction of stardust by thermal processing in the protoplanetary disk 7-9 or by aqueous alteration on parent bodies 10 , have all been proposed as possible mechanisms to generate isotope heterogeneity. While these individual processes can explain nucleosynthetic variations for specific elements, it is debated whether a unifying explanation for all elemental trends exists 11 . Therefore, considerable uncertainty remains as to which processes were important for dust processing in the protoplanet...

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Section: Mixing Interstellar Medium Grown Dust With Stardustmentioning

confidence: 99%

The origin of s-process isotope heterogeneity in the solar protoplanetary disk

Hunt

Lugaro

et al. 2019

Nat Astron

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“…An additional important source of uncertainty comes from the nuclear inputs adopted to calculate the r-process nucleosynthesis, the most important ones being nuclear masses, β-decay rates and nuclear fission models (Eichler et al 2015;Thielemann et al 2017). Finally, the observed evolution of the r-elements in the Galaxy is hard (albeit not impossible) to conciliate with our current understanding of the occurrence rate of NSMs, regarding both the early (halo) and the late (disk) phases of the Milky Way (Tsujimoto & Shigeyama 2014;Ishimaru et al 2015;Ojima et al 2018;Côté et al 2018;Hotokezaka et al 2018;Côté et al 2018;Guiglion et al 2018;Wehmeyer et al 2019;Siegel et al 2019;Haynes & Kobayashi 2019;Côté et al 2019).…”

Section: Introductionmentioning

confidence: 99%

Chemical evolution with rotating massive star yields II. A new assessment of the solar s- and r- process components

Prantzos

Abia

Cristallo

et al. 2019

Monthly Notices of the Royal Astronomical Society

129

155

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The decomposition of the Solar system abundances of heavy isotopes into their sand r-components plays a key role in our understanding of the corresponding nuclear processes and the physics and evolution of their astrophysical sites. We present a new method for determining the s-and r-components of the Solar system abundances, fully consistent with our current understanding of stellar nucleosynthesis and galactic chemical evolution. The method is based on a study of the evolution of the solar neighborhood with a state-of-the-art 1-zone model, using recent yields of low and intermediate mass stars as well as of massive rotating stars. We compare our results with previous studies and we provide tables with the isotopic and elemental contributions of the s-and r-processes to the Solar system composition.

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“…Typical elements produced by the r process include Eu, Os, Au and Pt. Different sites have been proposed to host the extreme conditions that are required for the r process, such as magneto-hydrodynamically driven supernovae (Ono et al 2012;Winteler et al 2012;Nishimura et al 2015Nishimura et al , 2017 and neutron star mergers (Lattimer & Schramm 1974;Meyer 1989;Thielemann et al 2017;Kilpatrick et al 2017;Côté et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Learning about the Intermediate Neutron-capture Process from Lead Abundances*

Hampel

Karakas

Stancliffe

et al. 2019

ApJ

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Lead (Pb) is predominantly produced by the slow neutron-capture process (s process) in asymptotic giant branch (AGB) stars. In contrast to significantly enhanced Pb abundances predicted by low-mass, low-metallicity AGB-models, observations of Magellanic post-AGB stars show incompatibly low Pb abundances. Observations of carbon-enhanced metal-poor (CEMP) stars whose s-process enrichments are accompanied by heavy elements traditionally associated with the rapid neutron-capture process (r process) have raised the need for a neutron-capture process operating at neutron densities intermediate to the s and r process: the so-called i process. We study i-process nucleosynthesis with single-zone nuclear-network calculations. Our i-process models can explain the heavy-element abundance patterns measured in Magellanic post-AGB stars including their puzzlingly low Pb abundances. Furthermore, the heavy-element enhancements in the post-AGB and CEMP-i stars, particularly their Pb abundance, allow us to characterise the neutron densities and exposures of the i process that produced the observed abundance patterns. We find that the lower-metallicity CEMP-i stars ([Fe/H] ≈ −2.5) have heavy-element abundances best matched by models with higher neutron densities and exposures (τ > 2.0 mbarn −1 ) compared to the higher-metallicity post-AGB stars ([Fe/H] ≈ −1.3, τ < 1.3 mbarn −1 ). This offers new constraints and insights regarding the properties of i-process sites and demonstrates that the responsible process operates on time scales of the order of a few years or less.

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The Origin of r-process Elements in the Milky Way

Cited by 226 publications

References 124 publications

The origin of s-process isotope heterogeneity in the solar protoplanetary disk

The origin of s-process isotope heterogeneity in the solar protoplanetary disk

Chemical evolution with rotating massive star yields II. A new assessment of the solar s- and r- process components

Learning about the Intermediate Neutron-capture Process from Lead Abundances*

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