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Nuclear transmutation is the conversion of one nuclide into another. It can occur by the radioactive decay of a nucleus, or the reaction of a nucleus with another particle. The first manmade nucleus was produced in Ernest Rutherford’s laboratory in 1919 by a transmutation reaction, the bombardment of one type of nuclei with other nuclei or with neutrons. Rutherford bombarded nitrogen-14 atoms with high-speed α particles from a natural radioactive isotope of radium and observed...
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In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis,  the precessing magnetic moments are randomly oriented around the z-axis.
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The number of nuclear spins aligned in the lower energy state is slightly greater than those in the higher energy state. In the presence of an external magnetic field, as the spins precess at the Larmor frequency, the excess population results in a net magnetization oriented along the z axis. When a pulse or a short burst of radio waves at the Larmor frequency is applied along the x axis, the coupling of frequencies causes resonance and flips the nuclear spins of the excess population from the...
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Magnets are commonly found in everyday objects, such as toys, hangers, elevators, doorbells, and computer devices. Experimentation on these magnets shows that all magnets have two poles: one is labeled north (N) and the other south (S). Magnetic poles repel if they are alike and attract if unlike. Moreover, both poles of a magnet attract unmagnetized pieces of iron.
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r-Process elements from magnetorotational hypernovae.

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Magnetorotational hypernovae, not just neutron-star mergers, likely created heavy elements in the early universe. Studying primitive stars reveals these crucial cosmic element factories and their connection to gamma-ray bursts.

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Area of Science:

  • Astronomy and Astrophysics
  • Nuclear Astrophysics
  • Cosmochemistry

Background:

  • Neutron-star mergers are confirmed sites for rapid-neutron-capture (r-process) element production.
  • Galactic chemical evolution models show neutron-star mergers alone cannot explain observed element abundances in metal-poor stars.
  • Chemically primitive stars in the Milky Way halo preserve early nucleosynthetic signatures, offering clues to unknown r-process sites.

Purpose of the Study:

  • To investigate potential alternative sites for r-process nucleosynthesis.
  • To analyze the element abundance pattern of the extremely metal-poor star SMSS J200322.54-114203.3.
  • To compare observed abundances with theoretical yields from different astrophysical events.

Main Methods:

  • Spectroscopic analysis of the extremely metal-poor star SMSS J200322.54-114203.3.
  • Measurement of element abundance patterns, focusing on r-process elements.
  • Comparison of observed abundance patterns with nucleosynthetic yields from a 25-solar-mass magnetorotational hypernova model.

Main Results:

  • The star SMSS J200322.54-114203.3 exhibits a significant enhancement of r-process elements at very low metallicity.
  • The observed element abundance pattern closely matches the predicted yields from a single 25-solar-mass magnetorotational hypernova.
  • This hypernova model accounts for the production of r-process, light, and iron-peak elements.

Conclusions:

  • Magnetorotational hypernovae are a viable and significant site for r-process nucleosynthesis in the early universe.
  • These hypernovae could explain the observed abundance patterns in metal-poor stars, resolving limitations of neutron-star merger-only models.
  • The association of hypernovae with long-duration gamma-ray bursts suggests these explosive events were important in early galactic chemical enrichment.