Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 445, Issue 3, Pages 2946-2983Publisher
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stu1977
Keywords
nuclear reactions, nucleosynthesis, abundances; stars: abundances; stars: atmospheres; stars: Population II
Categories
Funding
- ESO telescope at the La Silla Observatory [072.A-9002(A), 082.B-0386, 084.B-0666, 085.B-0765]
- Centre of Excellence in Astrophysics and Associated Technologies [PFB 06]
- PRIN MIUR
- DAGAL network from the People Programme (Marie Curie Actions) of the European Union [PITN-GA-2011-289313]
- CONICYT Anillo project [ACT-1122]
- BASAL [PFB-06]
- FONDECYT [1120013]
- CONICYT through FONDECYT [3140310]
- Division Of Astronomical Sciences
- Direct For Mathematical & Physical Scien [1211585] Funding Source: National Science Foundation
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We report the discovery of nine metal-poor stars with high levels of r-process enhancement (+0.81 <= [Eu/Fe] <= +1.13), including six subgiants and three stars on the red horizontal branch. We also analyse four previously known r-process-enhanced metal-poor red giants. From this sample of 13 stars, we draw the following conclusions. (1) High levels of r-process enhancement are found in a broad range of stellar evolutionary states, reaffirming that this phenomenon is not associated with a chemical peculiarity of red giant atmospheres. (2) Only 1 of 10 stars observed at multiple epochs shows radial-velocity variations, reaffirming that stars with high levels of r-process enhancement are not preferentially found among binaries. (3) Only 2 of the 13 stars are highly enhanced in C and N, indicating that there is no connection between high levels of r-process enhancement and high levels of C and N. (4) The dispersions in [Sr/Ba] and [Sr/Eu] are larger than the dispersions in [Ba/Eu] and [Yb/Eu], suggesting that the elements below the second r-process peak do not always scale with those in the rare Earth domain, even within the class of highly-r-process-enhanced stars. (5) The light-element (12 <= Z <= 30) abundances of highly-r-process-enhanced stars are indistinguishable from those with normal levels of r-process material at the limit of our data, 3.5 per cent (0.015 dex) on average. The nucleosynthetic sites responsible for the large r-process enhancements did not produce any detectable light-element abundance signatures distinct from normal core-collapse supernovae.
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