Identify the dominant r-process sources across all metallicities

Identify the dominant astrophysical sources responsible for r-process enrichment across the full stellar metallicity range, distinguishing the contributions of neutron star mergers, collapsars, and rare core-collapse supernovae.

Background

Multiple channels—neutron star mergers, collapsars, and rare core-collapse supernovae—have been proposed for r-process production, with differing delay times and environmental contexts. The paper emphasizes that, despite advances, the dominant source(s) across metallicities remains unresolved, and calls for future chemical evolution modeling to include enrichment timescales to address this question.

References

We finally note that the source of r-process enrichment at all metallicities remains an open, unanswered question.

— Where has all the $r$-process gone? Timescales for GRB-Kilonovae to Enrich their Host Galaxies  (2410.00095 - Nugent et al., 2024) in Section 5.4. r-Process Enrichment at Low Metallicity

Clearly, more efforts are needed to justify whether MRSNe can contribute significantly to the main Galactic $r$-process inventory.

— Supernova nucleosynthesis: a review  (2609.16584 - Zha et al., 15 Sep 2026) in Section 6.1, “Magnetorotational supernovae”

Therefore, whether collapsars are significant $r$-process contributors remains highly debated.

— Supernova nucleosynthesis: a review  (2609.16584 - Zha et al., 15 Sep 2026) in Section 6.2, “Collapsar”

Given the limited number of Eu detections and the detection threshold of our spectra, we do not draw a firm conclusion on the $r$-process enrichment level of the GES-associated stars in this sample.

— High Resolution Spectroscopic Follow-up Observation Results for 13 EMP Candidates Selected by Narrow-band Photometry  (2609.09645 - Chen et al., 9 Sep 2026) in Section 6.2, “Inspection with dynamically tagged groups”