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Table · dataset · 2021

Lanthanide fraction distribution of metal-poor stars

Listed in IVOA Registry (Virtual Observatory)

Multimessenger observations of the neutron star merger GW170817 and its kilonova proved that neutron star mergers can synthesize large quantities of r-process elements.

Description

If neutron star mergers in fact dominate all r-process element production, then the distribution of kilonova ejecta compositions should match the distribution of r-process abundance patterns observed in stars. The lanthanide fraction (X_La_) is a measurable quantity in both kilonovae and metal-poor stars, but it has not previously been explicitly calculated for stars.

Here we compute the lanthanide fraction distribution of metal-poor stars ([Fe/H]{<}-2.5) to enable comparison to current and future kilonovae. The full distribution peaks at log X_La_~-1.8, but r-process-enhanced stars ([Eu/Fe]>0.7) have distinctly higher lanthanide fractions: logX_La_>~-1.5. We review observations of GW170817 and find general consensus that the total logX_La_=-2.2+/-0.5, somewhat lower than the typical metal-poor star and inconsistent with the most highly r-enhanced stars.

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For neutron star mergers to remain viable as the dominant r-process site, future kilonova observations should be preferentially lanthanide-rich (including a population of ~10% with logX_La_>-1.5). These high-X_La_ kilonovae may be fainter and more rapidly evolving than GW170817, posing a challenge for discovery and follow-up observations. Both optical and (mid-)infrared observations will be required to robustly constrain kilonova lanthanide fractions.

If such high-X_La_ kilonovae are not found in the next few years, that likely implies that the stars with the highest r-process enhancements have a different origin for their r-process elements.

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concepts[field].anzsrc:group:5101enrichment · IVOA Registrytaxonomy-embedding@1.1.0title+keywords+description (70%)
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