Evidence for r-process Delay in Very Metal-poor Stars

Abstract The abundances of r -process elements very metal-poor stars capture the history enrichment in early stage star formation a galaxy. Currently, various types astrophysical sites including neutron mergers (NSMs), magneto-rotational supernovae, and collapsars, are suggested as origin elements. time delay between production is key to distinguish these scenarios, with caveat that diffusion interstellar medium may induce because events rare. Here we study observed Ba abundance data tracer We find gradual increase [Ba/Mg] [Fe/H], which remarkably similar among Milky Way classical dwarfs, Requires significant (100 Myr–1 Gyr) from rather than diffusion-induced delay. stress this conclusion robust assumption regarding s contamination sources no would overproduce at low metallicities, even without contribution -process. Therefore, conclude delay, possibly NSMs, origins