Neutron-Capture Elements in the Early Galaxy

Abstract

The content of neutron-capture (trans-iron-peak) elements in the lowmetallicity Galactic halo varies widely from star to star. The differences are both in bulk amount of the neutron-capture elements with respect to lighter ones and in element-to-element ratios among themselves. Several well-defined abundance distributions have emerged that reveal characteristic rapid and slow neutron-capture nucleosynthesis patterns. In this review we summarize these observed metal-poor star's abundances, contrasting them with the Solar-system values, comparing them to theoretical predictions, using them to assess the types of stars responsible for their specific anomalies, and speculating on the timing and nature of early Galactic nucleosynthesis. 241 Annu. Rev. Astro. Astrophys. 2008.46:241-288. Downloaded from www.annualreviews.org by Carleton University (Canada) on 09/20/13. For personal use only.

Origin of r-Process Elements and Galactic Chemodynamical Evolution

“…[5] and refs therein), and by observations of the detailed elemental abundance distributions observed in r-process enhanced metal-poor stars in the Galactic halo [6]. The elemental abundances for these stars appear to identically match the Solar-System r-process abundances.…”

“…Observations [6] showing the appearance of heavy-element r-process abundances early in the history of the Galaxy seem to favor the short stellar lifetime of CCSNe as the r-process site. However, identifying the r-process site in models of CCSNe has been difficult [20,21].…”

Short-Lived 244Pu Points to Neutron Star Binary Mergers as Sites for r-Process Nucleosynthesis

“…These elements show a uniform abundance pattern in metal-poor stars [12], suggesting that they are produced in a single kind of event. The total mass yields a relation between the Galactic event rate, R, and the heavy r-process mass produced in each event M ej,A≥90 (see Fig.…”

Nucleosynthesis in Supernovae, Hypernovae/Gamma-ray Bursts and Compact Binary Mergers

“…In the remaining part we want to focus here on the origin of the r-process. Abundances in low metallicity stars [23,60,66] seem to show two types of (extreme) patterns: (a) so-called Sneden stars come with a solar r-process pattern (i.e. the responsible site dominates the solar r-process and apparently produces it in each single event).…”