What are the astrophysical sites for the r-process and the production of heavy elements?

Thielemann, Friedrich‐Karl; Arcones, Almudena; Käppeli, Roger; Liebendörfer, M.; Rauscher, T.; Winteler, Christian; Fröhlich, C.; Dillmann, I.; Fischer, Tobias; Martı́nez-Pinedo, G.; Langanke, K.; Farouqi, K.; Kratz, K. L.; Panov, I. V.; Korneev, I. K.

doi:10.1016/j.ppnp.2011.01.032

Cited by 262 publications

(163 citation statements)

References 96 publications

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“…The astrophysical sites responsible for synthesizing the heaviest elements in the Universe via the rapid neutron capture process (rprocess, Burbidge et al 1957;Cameron 1957) have been debated for decades (for reviews, see Qian & Wasserburg 2007;Arnould et al 2007;Sneden et al 2008;Thielemann et al 2011).…”

Section: Introductionmentioning

confidence: 99%

Neutrino-heated winds from millisecond protomagnetars as sources of the weak r-process

Vlasov

Metzger

Lippuner

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We explore heavy element nucleosynthesis in neutrino-driven winds from rapidly-rotating, strongly magnetized proto-neutron stars ("millisecond proto-magnetars") for which the magnetic dipole is aligned with the rotation axis, and the field is assumed to be a static force-free configuration. We process the proto-magnetar wind trajectories calculated by Vlasov et al. (2014) through the r-process nuclear reaction network SkyNet using contemporary models for the evolution of the wind electron fraction during the proto-neutron star cooling phase. Although we do not find a successful second or third peak r-process for any rotation period P, we show that proto-magnetars with P ∼ 1 − 5 ms produce heavy element abundance distributions that extend to higher nuclear mass number than from otherwise equivalent spherical winds (with the mass fractions of some elements enhanced by factors of ∼ > 100 − 1000). The heaviest elements are synthesized by outflows emerging along flux tubes which graze the closed zone and pass near the equatorial plane outside the light cylinder. Due to dependence of the nucleosynthesis pattern on the magnetic field strength and rotation rate of the proto-neutron star, natural variations in these quantities between core collapse events could contribute to the observed diversity of the abundances of weak r-process nuclei in metal-poor stars. Further diversity, including possibly even a successful third-peak r-process, could be achieved for misaligned rotators with non-zero magnetic inclination with respect to the rotation axis. If proto-magnetars are central engines for GRBs, their relativistic jets should contain a high mass fraction of heavy nuclei of characteristic mass numberĀ ≈ 100, providing a possible source for ultra-high energy cosmic rays comprised of heavy nuclei with an energy spectrum that extends beyond the nominal GZK cut-off for protons or iron nuclei.

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Section: Introductionmentioning

confidence: 99%

Neutrino-heated winds from millisecond protomagnetars as sources of the weak r-process

Vlasov

Metzger

Lippuner

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…Observations [6] showing the appearance of heavy-element r-process abundances early in the history of the Galaxy seem to favor the short stellar lifetime of CCSNe as the r-process site. However, identifying the r-process site in models of CCSNe has been difficult [20,21].…”

Section: Current Models For the R-processmentioning

confidence: 99%

Origin of r-Process Elements and Galactic Chemodynamical Evolution

Mathews¹,

Shibagaki²,

Kajino³

2017

Proceedings of the 14th International Symposium on Nuclei in the Cosmos (NIC2016)

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It has been known for more than half a century that about half of the elements heavier than iron are produced via rapid neutron capture in the r-process. Indeed, the basic physical conditions for the r-process are well constrained by simple nuclear physics. In spite of this simplicity, however, the unambiguous identification of the site for the r-process nucleosynthesis has remained elusive. Parametrically, one can divide current models for the r-process into three scenarios roughly characterized by the number of neutron captures per seed nucleus (n/s). This parameter, in turn is the consequence of a variety of conditions such as time-scale, baryon density, average charge per baryon, and entropy. Here, we summarize various proposed sites for the r-process along with their short comings. Insights from a variety of nuclear physics measurements, astronomical observations, and models for galactic chemo-dynamical evolution are summarized. A paradigm is proposed whereby one may be able to quantify the relative contributions of each astrophysical site.

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“…They produce the so-called weak s-process elements [18]. The production of r-process remains at the moment quite uncertain, as for the p-process elements, but their synthesis is very likely related to massive star evolution either single or in close binaries [54][55][56].…”

Section: Introductionmentioning

confidence: 99%

Evolution and Nucleosynthesis of Massive Stars

Meynet¹,

Maeder²,

Choplin³

et al. 2017

Proceedings of the 14th International Symposium on Nuclei in the Cosmos (NIC2016)

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Massive stars are rapid nuclear reactors that play a key role in injecting new synthesized elements in the interstellar medium. Depending on the strengths of the stellar winds on the efficiency of mixing processes, the masses and the chemical compositions of their ejecta can be dramatically different. In a first part, we describe two types of rotating models differing by the physics involved and discussing various consequences. In a second part, we focus on the impacts of rotation in massive stars at very low metallicity. Various nucleosynthetic signatures pointing towards the need for some extra-mixing in the first generation of stars are presented. This extra-mixing has great chance to be driven by rotation for the following reasons : 1) when the metallicity decreases, the formation of fast rotators seem to be favored; 2) rotational mixing is more efficient at low metallicities; 3) primary nitrogen is produced only at low metallicities a fact that can be well explained by more efficient rotational mixing at low metallicities.

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What are the astrophysical sites for the r-process and the production of heavy elements?

Cited by 262 publications

References 96 publications

Neutrino-heated winds from millisecond protomagnetars as sources of the weak r-process

Neutrino-heated winds from millisecond protomagnetars as sources of the weak r-process

Origin of r-Process Elements and Galactic Chemodynamical Evolution

Evolution and Nucleosynthesis of Massive Stars

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