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r-Process elements from magnetorotational hypernovae
D Yong1,2, C Kobayashi3,4, G S Da Costa5,3
1Research School of Astronomy and Astrophysics, Australian National University, Canberra, Australian Capital Territory, Australia. david.yong@anu.edu.au.
Nature
|July 8, 2021
Summary
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.
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.
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