Kavli Affiliate: Anna Frebel
| First 5 Authors: Anna Frebel, Alexander P. Ji, , ,
| Summary:
This chapter presents an overview of the recent progress on spectroscopic
observations of metal-poor stars with r-process element signatures found in the
Milky Way’s stellar halo and satellite dwarf galaxies. Major empirical lessons
related to the origins of the r-process are discussed, including the
universality of the observed r-process pattern and deviations from universality
among the light r-process elements and actinides. Different astrophysical sites
of the r-process based on theoretical expectations are presented, including
common and rare supernovae and neutron star mergers. A major distinguishing
factor between r-process sites is their delay time distribution. The best
constraints on the detailed r-process pattern come from Galactic halo r-process
stars, but these cannot provide information on the environment of the stars’
birth gas clouds. Studying r-process enrichment within dwarf galaxies can
remedy the situation despite the fact that high-resolution spectroscopic
observations of individual stars in these systems are very difficult to obtain.
A general overview of dwarf galaxy properties and chemical evolution
expectations depending on their mass and star formation duration is provided.
The r-process trends depend on the stellar mass and star formation durations of
dwarf galaxies in a way that clearly shows that the r-process is rare,
prolific, and has both prompt and delayed sources. This work complements
ongoing theoretical heavy-element nucleosynthesis explorations and experimental
measurements of the properties of r-process nuclei, such as with the Facility
for Rare Isotope Beams.
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