Details

Autor(en) / Beteiligte

• 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

Titel

The R-Process Alliance: First Magellan/MIKE Release from the Southern Search for R-process-enhanced Stars

Ist Teil von

• The Astrophysical journal, 2020-08, Vol.898 (2), p.150

Ort / Verlag

Philadelphia: IOP Publishing

Erscheinungsjahr

2020

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• Abstract Extensive progress has recently been made in our understanding of heavy-element production via the r -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-poor r -process-enhanced stars provide key evidence for the dominant site(s) of the r -process and whether NSBMs are sufficiently frequent or prolific r -process sources to be responsible for the majority of r -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 the R -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 enhanced r -II (with [Eu/Fe] > +1.0), 62 new moderately enhanced r -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 new s -process-enhanced ([Ba/Eu] > +0.5) and five new r / 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 the r -II stars shows a deficit in α and Fe-peak elements, typical of dwarf galaxy stars. Our search for r -process-enhanced stars by RPA efforts has already roughly doubled the known r -process sample.