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TheR-Process Alliance: First Magellan/MIKE Release from the Southern Search forR-process-enhanced Stars*

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Ezzeddine, Rana ; Rasmussen, Kaitlin ; Frebel, Anna ; Chiti, Anirudh ; Hinojisa, Karina ; Placco, Vinicius M. ; Ji, Alexander P. ; Beers, Timothy C. ; Hansen, Terese T. ; Roederer, Ian U. ; Sakari, Charli M. ; Melendez, Jorge
Número total de Autores: 12
Tipo de documento: Artigo Científico
Fonte: ASTROPHYSICAL JOURNAL; v. 898, n. 2, p. 29-pg., 2020-08-01.
Resumo

Extensive progress has recently been made in our understanding of heavy-element production via ther-process in the universe, specifically with the first observed neutron star binary merger (NSBM) event associated with the gravitational-wave signal detected by LIGO, GW170817. The chemical abundance patterns of metal-poorr-process-enhanced stars provide key evidence for the dominant site(s) of ther-process and whether NSBMs are sufficiently frequent or prolificr-process sources to be responsible for the majority ofr-process material in the universe. We present atmospheric stellar parameters (using a nonlocal thermodynamic equilibrium analysis) and abundances from a detailed analysis of 141 metal-poor stars carried out as part of theR-Process Alliance (RPA) effort. We obtained high-resolution "snapshot" spectroscopy of the stars using the MIKE spectrograph on the 6.5 m Magellan Clay telescope at Las Campanas Observatory in Chile. We find 10 new highly enhancedr-II (with [Eu/Fe] > +1.0), 62 new moderately enhancedr-I (+0.3 < [Eu/Fe] <= +1.0), and 17 new limited-r([Eu/Fe] < +0.3) stars. Among those, we find 17 new carbon-enhanced metal-poor (CEMP) stars, of which five are CEMP-no. We also identify one news-process-enhanced ([Ba/Eu] > +0.5) and five newr/s(0.0 < [Ba/Eu] < +0.5) stars. In the process, we discover a new ultra-metal-poor (UMP) star at [Fe/H] = -4.02. One of ther-II stars shows a deficit in alpha and Fe-peak elements, typical of dwarf galaxy stars. Our search forr-process-enhanced stars by RPA efforts has already roughly doubled the knownr-process sample. (AU)

Processo FAPESP: 14/18100-4 - Populações estelares na Via Láctea: bojo, halo, disco e regiões de formação de estrelas; instrumentação para espectroscopia de alta resolução
Beneficiário:Beatriz Leonor Silveira Barbuy
Modalidade de apoio: Auxílio à Pesquisa - Temático