The lanthanide fraction distribution in metal-poor stars: a test of neutron star mergers as the dominant r-process site

Understand

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

• 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 (XLa) 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.