Mergers Fall Short: Nonmerger Channels Required for Galactic Heavy Element Production
5 affiliations
- 1The University of Texas at Austin
- 2University of Greifswald
- 3University of Guelph
- 4Stripe
- 5California State University Fullerton
Abstract
Since the discovery of the binary neutron star merger GW170817 and its associated kilonova, neutron star mergers have been established as a key production channel for r -process elements in the Universe. However, multiple lines of evidence, including the observations of r -process abundances as inferred from stellar spectra of Milky Way disk stars, suggest that additional channels may be needed to fully account for the r -process element enrichment in the Milky Way. Neutron star–black hole mergers and fast-merging binary neutron star systems are among the leading alternative candidates. In this paper, we combine gravitational-wave observations from LIGO–Virgo–KAGRA with data from short gamma-ray bursts, Galactic pulsars, and Galactic [Eu/Fe] versus [Fe/H] abundance observations to assess the contribution of these mergers to r -process enrichment in the Galactic disk. Our analysis employs a unified, likelihood-based inference framework that consistently propagates uncertainties in merger rates, delay-time distributions, mass- and spin-dependent ejecta yields, and stellar abundance measurements. We find that neither neutron star–black hole mergers nor fast-merging binary neutron star populations can dominate the additional prompt enrichment required by the disk-star data unless one invokes extreme assumptions about merger rates or yields. Within the adopted model, these results strongly favor a substantial prompt enrichment component beyond the merger channels considered here.
Related
- Aligned Hierarchical Black Hole Mergers in Active-Galactic-Nuclei Disks Revealed by GWTC-4
- Constraining Ultralight Scalars with Black Hole Binary Mergers in Galactic Nuclei
- Black Hole Binary Mergers in Galactic Nuclei: Combined Effects of Secular Dynamics and Stellar Flybys
- Black Hole Binary Mergers in Galactic Nuclei: Combined Effects of Secular Dynamics and Stellar Flybys
- Binary Dynamics and Mergers in a Stellar Disk and the Formation of Dusty Objects in the Galactic Center
BibTeX
@article{saleem2026mergers,
title = {{Mergers Fall Short: Nonmerger Channels Required for Galactic Heavy Element Production}},
author = {Muhammed Saleem and Hsin-Yu Chen and Daniel M. Siegel and Philippe Landry and Jocelyn S. Read and Kaile Wang},
journal = {The Astrophysical Journal},
year = {2026},
month = oct,
doi = {10.3847/1538-4357/aea6aa},
url = {https://iopscience.iop.org/article/10.3847/1538-4357/aea6aa},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Mergers Fall Short: Nonmerger Channels Required for Galactic Heavy Element Production
AU - Muhammed Saleem
AU - Hsin-Yu Chen
AU - Daniel M. Siegel
AU - Philippe Landry
AU - Jocelyn S. Read
AU - Kaile Wang
PY - 2026
DA - 2026/10/08
JO - The Astrophysical Journal
DO - 10.3847/1538-4357/aea6aa
UR - https://iopscience.iop.org/article/10.3847/1538-4357/aea6aa
AB - Since the discovery of the binary neutron star merger GW170817 and its associated kilonova, neutron star mergers have been established as a key production channel for r -process elements in the Universe. However, multiple lines of evidence, including the observations of r -process abundances as inferred from stellar spectra of Milky Way disk stars, suggest that additional channels may be needed to fully account for the r -process element enrichment in the Milky Way. Neutron star–black hole mergers and fast-merging binary neutron star systems are among the leading alternative candidates. In this paper, we combine gravitational-wave observations from LIGO–Virgo–KAGRA with data from short gamma-ray bursts, Galactic pulsars, and Galactic [Eu/Fe] versus [Fe/H] abundance observations to assess the contribution of these mergers to r -process enrichment in the Galactic disk. Our analysis employs a unified, likelihood-based inference framework that consistently propagates uncertainties in merger rates, delay-time distributions, mass- and spin-dependent ejecta yields, and stellar abundance measurements. We find that neither neutron star–black hole mergers nor fast-merging binary neutron star populations can dominate the additional prompt enrichment required by the disk-star data unless one invokes extreme assumptions about merger rates or yields. Within the adopted model, these results strongly favor a substantial prompt enrichment component beyond the merger channels considered here.
SN - 0004-637X
SN - 1538-4357
ER -