The role of fission in the r-process

Martı́nez-Pinedo, G.; Mocelj, D.; Zinner, N. T.; Kelić, A.; Langanke, K.; Panov, I. V.; Pfeiffer, B.; Rauscher, T.; Schmidt, Karl‐Heinz; Thielemann, Friedrich‐Karl

doi:10.1016/j.ppnp.2007.01.018

Cited by 78 publications

(52 citation statements)

References 30 publications

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“…The abundances of several isotopes ( 86 Sr, 93 Nb, 96 Mo, 100 Ru, 104 Pd, 110 Cd) could not be explained by adding s-and r-process (as observed in UMP stars) contributions. They suggested that these isotopes are produced by the Lighter Element Primary Process (LEPP), but they did not specify the astrophysical site nor the nuclear reactions involved.…”

Section: Lighter Heavy Elements: Sr Y Zrmentioning

confidence: 85%

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Neutrino-driven wind simulations and nucleosynthesis of heavy elements

Arcones

Thielemann

2012

J. Phys. G: Nucl. Part. Phys.

195

201

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Abstract. Neutrino-driven winds, which follow core-collapse supernova explosions, present a fascinating nuclear astrophysics problem that requires understanding advanced astrophysics simulations, the properties of matter and neutrino interactions under extreme conditions, the structure and reactions of exotic nuclei, and comparisons against forefront astronomical observations. The neutrino-driven wind has attracted vast attention over the last 20 years as it was suggested to be a candidate for the astrophysics site where half of the heavy elements are produced via the r-process. In this review, we summarize our present understanding of neutrino-driven winds from the dynamical and nucleosynthesis perspectives. Rapid progress has been made during recent years in understanding the wind with improved simulations and better micro physics. The current status of the fields is that hydrodynamical simulations do not reach the extreme conditions necessary for the r-process and the proton or neutron richness of the wind remains to be investigated in more detail. However, nucleosynthesis studies and observations point already to neutrino-driven winds to explain the origin of lighter heavy elements, such as Sr, Y, Zr.

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Section: Lighter Heavy Elements: Sr Y Zrmentioning

confidence: 85%

“…Neutrino-induced fission has been investigated in Ref. [102], but found to be negligible in neutrino-driven wind environments [103,104].…”

Section: Impact Of Nuclear Physics Input On the R-processmentioning

confidence: 99%

Neutrino-driven wind simulations and nucleosynthesis of heavy elements

Arcones

Thielemann

2012

J. Phys. G: Nucl. Part. Phys.

195

201

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“…For application in r-process simulations the (n, f )-reaction rates (which are the focus of the present paper) will have to be multiplied by the displayed percentages for obtaining a production rate of a specific fragment nucleus (Kelić et al 2005;Martínez-Pinedo et al 2007;Panov et al 2008). …”

Section: Fission Fragment Distributionsmentioning

confidence: 99%

“…In early applications to astrophysical nucleosynthesis, usually only one mode was considered, beta-delayed fission (Thielemann et al 1983) or a phenomenological model of spontaneous fission (Goriely & Clerbaux 1999;Freiburghaus et al 1999;Cowan et al 1999). However, it was shown recently that Tables 3-18 with these data are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/513/A61 neutron-induced fission is more important than beta-delayed fission in r-process nucleosynthesis (Panov & Thielemann 2003, 2004Martínez-Pinedo et al 2007). Thus, the need to provide a compilation of neutron-induced fission rates is obvious.…”

Section: Introductionmentioning

confidence: 99%

Neutron-induced astrophysical reaction rates for translead nuclei

Panov

Korneev

Rauscher

et al. 2010

A&A

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119

107

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Neutron-induced reaction rates, including fission and neutron capture, are calculated in the temperature range 10 8 ≤ T (K) ≤ 10 10 within the framework of the statistical model for targets with the atomic number 84 ≤ Z ≤ 118 (from Po to Uuo) from the neutron to the proton drip-line. Four sets of rates have been calculated, utilizing -where possible -consistent nuclear data for neutron separation energies and fission barriers from Thomas-Fermi (TF), Extended Thomas-Fermi plus Strutinsky Integral (ETFSI), Finite-Range Droplet Model (FRDM) and Hartree-Fock-Bogolyubov (HFB) predictions. Tables of calculated values as well as analytic seven parameter fits in the standard REACLIB format are supplied. We also discuss the sensitivity of the rates to the input, aiming at a better understanding of the variations introduced by the nuclear input.

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“…Progress in explaining observations is continually ongoing (Nomoto et al 2006) with fission readily recognized as being an important cutoff mechanism in r-process actinide growth process (Martinez-Penedo et al 2007). …”

Section: Actinide Genesis and Evolutionmentioning

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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The role of fission in the r-process

Cited by 78 publications

References 30 publications

Neutrino-driven wind simulations and nucleosynthesis of heavy elements

Neutrino-driven wind simulations and nucleosynthesis of heavy elements

Neutron-induced astrophysical reaction rates for translead nuclei

Nuclear criticality as a contributor to gamma ray burst events

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