S19A0007abst
S19A0007
Our success in Subaru observations on the Draco dSph has identified two r-process events that enriched gases at levels that differ by more than one order of magnitude. This finding poses two possibilities: neutron star mergers (NSMs), r-process site evidenced by GW170187’ counterparts, generate a largely different amount of r-process elements, or another r-process site, core-collapse supernovae (CCSNe), is present. To answer this question, the delay time of ejection of r-process elements elapsed from a birth of the progenitor star is a decisive ingredient to discriminate two candidates for r-process site: CCSNe or NSMs give a negligibly short or long timescale, respectively. This perspective predicts the difference in the metallicity at the time of occurrences of r-process events in the Sextans dSph which has a similar mass and metallicity to the Draco’s but is implied to experience a slower chemical enrichment than that of Draco: CCSN predicts a similar [Fe/H] to that of Draco whereas NSM predicts a lower [Fe/H]. Here we propose to measure Ba abundances for 17 Sextans stars ([Fe/H]<−2), detect r-process events, determine their occurrence metallicities, and identify the site of r-process events by comparison with S16A-097’s result on Draco. This is a second trial of S18A-25 due to a bad weather and earthquakes.
This document was translated from LATEX by HEVEA.