S18A0025abst
S18A0025
Our successful Subaru observations on the Draco dwarf spheroidal galaxy (dSph) have identified two r-process events that enriched gases at levels that differ by more than one order of magnitude. This finding leaves open two options for explaining the varying amount of nucleosynthesis products: either a single site generated a different amount of nucleosynthesis products or two distinct r-process sites were 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: core-collapse supernovae (CCSN) or neuron star mergers (NSM) gives a negligibly short or long (∼ 1Gyr) 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 predcits less [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 the S16A-097 result on Draco.
This document was translated from LATEX by HEVEA.