The r-process nucleosynthesis: a continued challenge for nuclear physics and astrophysics

Goriely, Stéphane; Demetriou, P.; Janka, Hans‐Thomas; Pearson, J. M.; Samyn, M.

doi:10.1016/j.nuclphysa.2005.05.107

Cited by 90 publications

(103 citation statements)

References 21 publications

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“…The decompression of dynamically ejected neutron-rich crust matter from NS-NS (or BH-NS) mergers was suggested to be an alternative or additional r-process site (Lattimer & Schramm 1974Lattimer et al 1977;Meyer 1989;Freiburghaus et al 1999;Goriely et al 2005Goriely et al , 2011. Hyper-massive NSs (HMNSs) resulting immediately after NS-NS merging (e.g., Sekiguchi et al 2011;Rezzolla et al 2011;Bauswein & Janka 2011), giving rise to magnetically driven and neutrino-driven outflows for ∼10-100 ms, are also suggested to eject r-processed material (Dessart et al 2009).…”

Section: Introductionmentioning

confidence: 99%

Ther-PROCESS IN THE NEUTRINO-DRIVEN WIND FROM A BLACK-HOLE TORUS

Wanajo

Janka

2012

ApJ

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We examine r-process nucleosynthesis in the neutrino-driven wind from the thick accretion disk (or "torus") around a black hole. Such systems are expected as remnants of binary neutron star or neutron star-black hole mergers. We consider a simplified, analytic, time-dependent evolution model of a 3 M central black hole surrounded by a neutrino emitting accretion torus with 90 km radius, which serves as basis for computing spherically symmetric neutrino-driven wind solutions. We find that ejecta with modest entropies (∼30 per nucleon in units of the Boltzmann constant) and moderate expansion timescales (∼100 ms) dominate in the mass outflow. The mass-integrated nucleosynthetic abundances are in good agreement with the solar system r-process abundance distribution if a minimal value of the electron fraction at the charged-particle freezeout, Y e,min ∼ 0.2, is achieved. In the case of Y e,min ∼ 0.3, the production of r-elements beyond A ∼ 130 does not reach to the third peak but could still be important for an explanation of the abundance signatures in r-process deficient stars in the early Galaxy. The total mass of the ejected r-process nuclei is estimated to be ∼1× 10 −3 M . If our model was representative, this demands a Galactic event rate of ∼2 × 10 −4 yr −1 for black-hole-torus winds from merger remnants to be the dominant source of the r-process elements. Our result thus suggests that black-hole-torus winds from compact binary mergers have the potential to be a major, but probably not the dominant, production site of r-process elements.

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Section: Introductionmentioning

confidence: 99%

Ther-PROCESS IN THE NEUTRINO-DRIVEN WIND FROM A BLACK-HOLE TORUS

Wanajo

Janka

2012

ApJ

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“…Other models considering actinide genesis include neutron star mergers (Goriely et al 2005) and neutron star, black hole mergers (Domainco and Ruffert 2005). This process alone would generate substantial gamma ray spectral lines from an abundance of transuranics generated but not necessarily the criticality event prompt gamma distribution directly followed by a delayed fission product decay gamma spectra.…”

Section: Actinide Genesis and Evolutionmentioning

confidence: 99%

“…In this way, the most metal poor stars end up with the lowest angular momentum orbits in a galaxy. Chemical fractionation of lighter elements and in particular, smaller organic molecules seem to be quantitatively predictive based on current models (Dishoeck and Blake 1998) although no detailed chemical dynamics for heavy metals is currently able to produce highly compelling results.Other models considering actinide genesis include neutron star mergers (Goriely et al 2005) and neutron star, black hole mergers (Domainco and Ruffert 2005). This process alone would generate substantial gamma ray spectral lines from an abundance of transuranics generated but not necessarily the criticality event prompt gamma distribution directly followed by a delayed fission product decay gamma spectra.…”

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confidence: 99%

Nuclear criticality as a contributor to gamma ray burst events

Hayes¹

2013

Astrophys Space Sci

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-Most gamma ray bursts are able to be explained using supernovae related phenomenon. Some measured results still lack compelling explanations and a contributory cause from nuclear criticality is proposed. This is shown to have general properties consistent with various known gamma ray burst properties. The galactic origin of fast rise exponential decay gamma ray bursts is considered a strong candidate for these types of events. BackgroundThe Oklo uranium mine in South Africa is a place where the natural abundance of U235 was found to be consistently less than the 0.72% found everywhere else on the planet (with the remainder of the uranium being almost entirely U238). It was not until the excess isotopic distribution from the stable fission product decay nuclides was found that it was realized this was an ancient natural nuclear reactor (Cowan 1976). Because the half life of U235 is almost an order of magnitude smaller than that of U238, the ratio of U235 to U238 increases in reverse time. By going back far enough in time, the abundance of the two nuclides would become comparable. With sufficiently enriched uranium in the soil, addition of moisture from rain would then provide the necessary moderation for the earth to sustain a natural nuclear chain reaction until the heat would drive away the water and return the system to a subcritical state. This process is believed to have occurred over a billion years ago in central Africa (Fujii et al. 2000).If the Oklo reactor occurred naturally as a result of uranium created in supernovae (SN) events, it is not incredible to think that it could occur prior to accumulation into planetary form from other SN events. In other words, just after the SN creation of the uranium and transuranic isotopes, most of the already radioactive elements created will quickly decay into stable atoms leaving these fissile and fissionable isotopes close to their original abundance. Even if a large fraction of the Pu239 (which is fissile with a moderately long half life of just over 24 ka) were to decay away, there would still be almost the initial amount of U233 (which is fissile with a moderately long half life of just under 0.2 ma) with only a negligible fraction of the U235 having decayed away. If a gravitational accumulation of the SN excreta were to occur within some few years, a longer list of potential fissile isotopes could be present in the material including Pu241, Am243, Cm243, Cm245, Cm247, etc while the majority of the radioactive elements would still have decayed into stable isotopes. This presents a dynamic reactivity dependency in terms of the fissile nuclides generated which would be strongly dependent on the initial isotopic distribution source term.The model presented here has the potential to explain some of the highly varied nature of a portion of measured gamma ray bursts (GRBs). These include the random nature of the events in terms of their parametric values and ranges. Specifically many measured values of energy and time distributions, pulsing, and afterglows ...

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“…15,16 Recently, special attention has been paid to NS mergers following the confirmation by hydrodynamic simulations that a non-negligible amount of matter can be ejected [17][18][19] and the confirmation that such material should be enriched in r-process nuclei. [20][21][22] The ejection of initially cold, decompressed NS matter might also happen in other astrophysical scenarios like giant flares in soft-gamma repeaters, the explosion of a NS eroded below its minimum mass, or the equatorial shedding of material from very rapidly rotating supramassive or ultramassive NSs (see Ref. 11 for more details).…”

Section: The R-processmentioning

confidence: 99%

Nucleosynthesis: a field with still many open nuclear physics questions

Goriely

Susa²,

Arnould³

et al. 2010

AIP Conference Proceedings

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Stellar nucleosynthesis is a vastly interdisciplinary field. There is a large number of different problems invoked calling for a variety of different and complementary research fields. Impressive progress has been made for the last decades in the various fields related to nucleosynthesis, especially in experimental and theoretical nuclear physics, as well as in ground-based or space astronomical observations and astrophysical modellings. In spite of that success, major problems and puzzles remain. The three major nucleosynthesis processes called for to explain the origin of the elements heavier than iron are described and the major pending questions discussed. As far as nuclear physics is concerned, good quality nuclear data is known to be a necessary condition for a reliable modelling of stellar nucleosynthesis. Through some specific examples, the need for further theoretical or experimental developments is also critically discussed in view of their impact on nucleosynthesis predictions.

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The r-process nucleosynthesis: a continued challenge for nuclear physics and astrophysics

Cited by 90 publications

References 21 publications

Ther-PROCESS IN THE NEUTRINO-DRIVEN WIND FROM A BLACK-HOLE TORUS

Ther-PROCESS IN THE NEUTRINO-DRIVEN WIND FROM A BLACK-HOLE TORUS

Nuclear criticality as a contributor to gamma ray burst events

Nucleosynthesis: a field with still many open nuclear physics questions

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