Kavli Affiliate: Anna Frebel
| First 5 Authors: Avrajit Bandyopadhyay, Rana Ezzeddine, Carlos Allende Prieto, Nima Aria, Shivani P. Shah
| Summary:
Understanding the abundance pattern of metal-poor stars and the production of
heavy elements through various nucleosynthesis processes offers crucial
insights into the chemical evolution of the Milky Way, revealing primary sites
and major sources of rapid neutron-capture process ($r$-process) material in
the Universe. In this fifth data release from the $R$-Process Alliance, we
present the detailed chemical abundances of 41 faint (down to V = 15.8) and
extremely metal-poor (down to [Fe/H] = -3.3) halo stars selected from the
$R$-Process Alliance (RPA). We obtained high-resolution spectra for these
objects with the HORuS spectrograph on the Gran Telescopio Canarias. We measure
the abundances of light, alpha, Fe-peak, and neutron-capture elements. We
report the discovery of five CEMP, one limited-$r$, three $r$-I, and four
$r$-II stars, and six Mg-poor stars. We also identify one star of a possible
globular cluster origin at an extremely low metallicity at [Fe/H] = -3.0. This
adds to the growing evidence of a lower limit metallicity floor for globular
cluster abundances. We use the abundances of Fe-peak elements and the
alpha-elements to investigate the contributions from different nucleosynthesis
channels in the progenitor supernovae. We find the distribution of [Mg/Eu] as a
function of [Fe/H] to have different enrichment levels, indicating different
possible pathways and sites of their production. We also reveal differences in
the trends of the neutron-capture element abundances of Sr, Ba, and Eu of
various r-I and r-II stars from the RPA data releases, which provide
constraints on their nucleosynthesis sites and subsequent evolution.
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