Chemical characteristics of three stellar streams

Abstract

In this thesis, we present high-resolution spectra of stars of three different stellar stream; Helmi debris stream, Helmi trail stream and [omega] Centauri stream. These stars have metallicities ranging from -3.05 < [Fe/HJ < -1.25 and magnitudes ranging from 9 < V < 13.5, thereby classifying them as bright metal-poor stars. We report detailed chemical abundance signatures of light fusion elements and heavy neutron-capture elements. We find that all three streams contain stars with r-process abundance signatures. Additionally, three star show a clear combined r+s-process enhancement. Those stars likely formed from a r-process enhanced gas and then experienced a s-process mass-transfer by a binary companion. Given the occurrence of r-process enhanced stars in all three streams, it is likely that the progenitors of these streams must have been similar in nature to ultra-faint r-process dwarf galaxies like Tucana III and Reticulum II, which were enriched in r-process elements by one neutron star merger or another prolific r-process source at the earliest times.