Kavli Affiliate: Anna Frebel
| First 5 Authors: Xiaowei Ou, Alexander P. Ji, Anna Frebel, Rohan P. Naidu, Guilherme Limberg
| Summary:
Neutron star mergers (NSMs) produce copious amounts of heavy r-process
elements after a time delayed inspiral process. Once NSMs are present in a
galaxy, r-process elements, such as Eu, are expected to significantly increase
with time. Yet, there has been limited observational data in support of Eu
increasing within Local Group galaxies. We have obtained high-resolution
Magellan/MIKE observations of 43 metal-poor stars in the Gaia-Sausage/Enceladus
tidally disrupted galaxy with $-2.5 < rm{[Fe/H]} < -1$. For the first time, we
find a clear rise in [Eu/Mg] with increasing [Mg/H] within one galaxy. We use a
chemical evolution model to study how such a rise can result from the interplay
of prompt and delayed r-process enrichment events. Delayed r-process sources
are required to explain the rise and subsequent leveling off of [Eu/Mg] in this
disrupted galaxy. However, the rise may be explained by delayed r-process
sources with either short ($sim 10$ Myr) or long ($sim 500$ Myr) minimum
delay times. Future studies on the nature of r-process sources and their
enrichment processes in the GSE will require additional stars in the GSE at
even lower metallicities than the present study.
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