The r-process of stellar nucleosynthesis: Astrophysics and nuclear physics achievements and mysteries

By M. Arnould, S. Goriely, Kohji Takahashi. 2007

700 citations recorded by the source corpus.

Abstract The r-process, or the rapid neutron-capture process, of stellar nucleosynthesis is called for to explain the production of the stable (and some long-lived radioactive) neutron-rich nuclides heavier than iron that are observed in stars of various metallicities, as well as in the solar system. A very large amount of nuclear information is necessary in order to model the r-process. This concerns the static characteristics of a large variety of light to heavy nuclei between the valley of stability and the vicinity of the neutron-drip line, as well as their beta-decay branches or their reactivity. Fission probabilities of very neutron-rich actinides have also to be known in order to determine the most massive nuclei that have a chance to be involved in the r-process. Even the properties of asymmetric nuclear matter may enter the problem. The enormously challenging experimental and theoretical task imposed by all these requirements is reviewed, and the state-of-the-art development in the field is presented. Nuclear-physics-based and astrophysics-free r-process models of different levels of sophistication have been constructed over the years. We review their merits and their shortcomings. The ultimate goal of r-process studies is clearly to identify realistic sites for the development of the r-process. Here too, the challenge is enormous, and the solution still eludes us. For long, the core collapse supernova of massive stars has been envisioned as the privileged r-process location. We present a brief summary of the one- or multidimensional spherical or non-spherical explosion simulations available to-date. Their predictions are confronted with the requirements imposed to obtain an r-process. The possibility of r-nuclide synthesis during the decompression of the matter of neutron stars following their merging is also discussed. Given the uncertainties remaining on the astrophysical r-process site and on the involved nuclear physics, any confrontation between predicted r-process yields and observed abundances is clearly risky. A comparison dealing with observed r-nuclide abundances in very metal-poor stars and in the solar system is attempted on grounds of r-process models based on parametrised astrophysics conditions. The virtues of the r-process product actinides for dating old stars or the solar system are also critically reviewed.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/4ffa53e413ca5b618eab9fbf74c676e253244b95

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Citations in the corpus

Signatures of hypermassive neutron star lifetimes on r-process nucleosynthesis in the disc ejecta from neutron star mergers (2017, methodology): “Using the solar r-process abundances from Arnould et al. (2007), we find log Y1st, /Y2nd, = +1.3, log YRE, /Y2nd, = −1.1, and log Y3rd, /Y2nd, = −0.42, which we use to normalize the values shown in Table 2.”
Mean field and beyond description of nuclear structure with the Gogny force: a review (2018, background): “Therefore, an accurate modeling of the properties of those exotic nuclear systems, like their masses, is mandatory in order to improve astrophysical predictions [38].”
The stellar halo of the Galaxy (2008, background): “It should be stressed, however, that the exact sites and conditions under which the various neutron-capture elements are produced, particularly at very low metallicities, are still somewhat uncertain (Travaglio et al. 2004; Arnould et al. 2007).”
The Origin of r-process Elements in the Milky Way (2017, background): “Second column: mass fractions Xobs in the solar r-process residuals (Arnould et al. 2007).”
Improved predictions of nuclear reaction rates with the TALYS reaction code for astrophysical applications (2008, background): “The readers are referred to Aikawa et al. (2005), Arnould& Goriely (2006) and Arnould et al. (2007) for a discussion on how nuclear models affect the reaction rates of relevance to nucleosynthesis.”
r-PROCESS NUCLEOSYNTHESIS IN DYNAMICALLY EJECTED MATTER OF NEUTRON STAR MERGERS (2011, background): “In Goriely et al. (2005) and Arnould et al. (2007) the thermodynamic profiles were constructed by a simple decompression model (see Goriely et al. 2011), but the neutron enrichment (or equivalently the electron fraction Ye) was consistently taken from β-equilibrium assumed to have been achieved at…”
Radioactive decays at limits of nuclear stability (2011, background): “…direct need for beta-decay data in astrophysics arises in processes where weak interactions play a role, either directly as beta decay rates or indirectly where neutrino interactions are important, see (Arnould et al., 2007; Borzov, 2006; Grawe et al., 2007; Langanke and Martínez-Pinedo, 2003).”
RADIOACTIVITY AND THERMALIZATION IN THE EJECTA OF COMPACT OBJECT MERGERS AND THEIR IMPACT ON KILONOVA LIGHT CURVES (2016, background): “Mergers may also produce optical/infrared transients (Li & Paczyński 1998; Metzger et al. 2010; Roberts et al. 2011; Barnes & Kasen 2013) powered by the radioactive decay of heavy elements synthesized via rapid neutron capture(the r-process; Arnould et al. 2007).”
Neutron Star Mergers Might Not Be the Only Source of r-process Elements in the Milky Way (2018, background): “Yields for low- and intermediate-mass stars, massive stars, SNe Ia, and NSNS mergers are taken from Ritter et al. (2018b), Nomoto et al. (2013), Iwamoto et al. (1999), and Arnould et al. (2007), respectively.”
THE r-PROCESS NUCLEOSYNTHESIS IN THE VARIOUS JET-LIKE EXPLOSIONS OF MAGNETOROTATIONAL CORE-COLLAPSE SUPERNOVAE (2015, background): “…which provide suitable neutron-rich conditions, are still undetermined, although a large amount of effort by nuclear physicists, astrophysicists, and astronomers has been devoted since the dawn of modern science (for the most recent status, see, Arnould et al. 2007; Thielemann et al. 2011).”