Using failed supernovae to constrain the Galactic r-process element production

Wehmeyer, B; Wehmeyer, B.; Fröhlich, C; Fröhlich, C.; Côté, B; Côté, B.; Pignatari, M; Pignatari, M.; Thielemann, F-K; Thielemann, F. K.

Abstract

Rapid neutron capture process (r-process) elements have been detected in a large fraction of metal-poor halo stars, with abundances relative to iron (Fe) that vary by over two orders of magnitude. This scatter is reduced to less than a factor of 3 in younger Galactic disc stars. The large scatter of r-process elements in the early Galaxy suggests that the r-process is made by rare events, like compact binary mergers and rare sub-classes of supernovae. Although being rare, neutron star mergers alone have difficulties to explain the observed enhancement of r-process elements in the lowest metallicity stars compared to Fe. The supernovae producing the two neutron stars already provide a substantial Fe abundance where the r-process ejecta from the merger would be injected. In this work we investigate another complementary scenario, where the r-process occurs in neutron star-black hole mergers in addition to neutron star mergers. Neutron star-black hole mergers would eject similar amounts of r-process matter as neutron star mergers, but only the neutron star progenitor would have produced Fe. Furthermore, a reduced efficiency of Fe production from single stars significantly alters the age–metallicity relation, which shifts the onset of r-process production to lower metallicities. We use the high-resolution [(20 pc)3/cell] inhomogeneous chemical evolution tool ‘ICE’ to study the outcomes of these effects. In our simulations, an adequate combination of neutron star mergers and neutron star-black hole mergers qualitatively reproduces the observed r-process abundances in the Galaxy.

Citation

Wehmeyer, B., Wehmeyer, B., Fröhlich, C., Fröhlich, C., Côté, B., Côté, B., Pignatari, M., Pignatari, M., Thielemann, F.-K., & Thielemann, F. K. (2019). Using failed supernovae to constrain the Galactic r-process element production. Monthly notices of the Royal Astronomical Society, 487(2), 1745-1753. https://doi.org/10.1093/mnras/stz1310

• Journal Article Type: Article
• Acceptance Date: May 5, 2019
• Online Publication Date: May 16, 2019
• Publication Date: Aug 1, 2019
• Deposit Date: Jun 19, 2019
• Publicly Available Date: Jun 19, 2019
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 487
• Issue: 2
• Pages: 1745-1753
• DOI: https://doi.org/10.1093/mnras/stz1310
• Keywords: Space and Planetary Science; Astronomy and Astrophysics
• Public URL: https://hull-repository.worktribe.com/output/2012973
• Publisher URL: https://academic.oup.com/mnras/article/487/2/1745/5490380
• Contract Date: Jun 19, 2019