Evidence from Disrupted Halo Dwarfs that $r$-process Enrichment via Neutron Star Mergers is Delayed by $\gtrsim500$ Myrs

Understand

The astrophysical origins of $r$-process elements remain elusive.

• Neutron star mergers (NSMs) and special classes of core-collapse supernovae (rCCSNe) are leading candidates.
• Due to these channels' distinct characteristic timescales (rCCSNe: prompt, NSMs: delayed), measuring $r$-process enrichment in galaxies of similar mass, but differing star-formation durations might prove informative.
• Two recently discovered disrupted dwarfs in the Milky Way's stellar halo, Kraken and \textit{Gaia}-Sausage Enceladus (GSE), afford precisely this opportunity: both have $M_{\star}\approx10^{8}M_{\rm{\odot}}$, but differing star-formation durations of ${\approx}2$ Gyrs and ${\approx}3.6$ Gyrs.