Abstract
In rapid neutron capture, or r-process, nucleosynthesis, heavy elements are built up via a sequence of neutron captures and beta decays that involves thousands of nuclei far from stability. Though we understand the basics of how the r-process proceeds, its astrophysical site is still not conclusively known. The nuclear network simulations we use to test potential astrophysical scenarios require nuclear physics data (masses, beta decay lifetimes, neutron capture rates, fission probabilities) for all of the nuclei on the neutron-rich side of the nuclear chart, from the valley of stability to the neutron drip line. Here we discuss recent sensitivity studies that aim to determine which individual pieces of nuclear data are the most crucial for r-process calculations. We consider three types of astrophysical scenarios: a traditional hot r-process, a cold r-process in which the temperature and density drop rapidly, and a neutron star merger trajectory.
Highlights
One of the major open questions in nuclear astrophysics is the site of the formation of the heaviest elements in the r-process of nucleosynthesis
Modern simulations of neutron star mergers, on the other hand, show robustly neutronrich outflows with vigorous r-processing [10, 11], and there may even be a hint of the radioactive decay of r-process material observed in a merger event [12]
In the cold r process, the temperature drops so quickly that equilibrium fails before even the A ∼ 195 peak is formed, and photodissociation plays almost no role in the subsequent dynamics
Summary
One of the major open questions in nuclear astrophysics is the site of the formation of the heaviest elements in the r-process of nucleosynthesis (for a review, see e.g., [1]). We have developed a program of r-process sensitivity studies to determine which of the thousands of pieces of nuclear data needed should be the targets of new experimental campaigns. We review the notable features of the sensitivity study results for separate nuclear mass, βdecay rate, and neutron capture rate sensitivity studies for a main (120 < A < 200) hot r process. These studies start with a single set of astrophysical conditions and point out the most important pieces of nuclear data for those conditions. We repeat our sensitivity studies assuming two additional distinct types of astrophysical conditions: a neutrino-driven wind cold r process, where the temperature and density drop quickly and equilibrium between captures and photodissociations, (n, γ)-(γ, n) equilibrium, holds only briefly, and a low entropy, very neutron-rich r process from a neutron star merger simulation
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