The R-Process Alliance: chemical abundances for a trio of R-process-enhanced stars -- one strong, one moderate, and one mild
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Cain_2018_ApJ_864_43.pdf
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Author(s)
Cain, Madelyn
Frebel, Anna
Gull, Maude
Ji, Alexander P.
Placco, Vinicius M.
Beers, Timothy C.
Meléndez, Jorge
Ezzeddine, Rana
Casey, Andrew R.
Hansen, Terese T.
Date Issued
September 2018
Journal
Astrophysical journal
Publisher
American Astronomical Society
Citation
Cain, Madelyn, et al., "The R-Process Alliance: chemical abundances for a trio of R-process-enhanced stars -- one strong, one moderate, and one mild." Astrophysical journal 864, 1 (September 2018): no. 43 doi 10.3847/1538-4357/AAD37D ©2018 Author(s)
Version
Final published version
Abstract
We present detailed chemical abundances of three new bright (V ∼ 11), extremely metal-poor ([Fe/H] ∼-3.0), r-process-enhanced halo red giants based on high-resolution, high-S/N Magellan/MIKE spectra. We measured abundances for 20-25 neutron-capture elements in each of our stars. J1432-4125 is among the most r-process-rich r-II stars, with [Eu/Fe] = +1.44 ± 0.11. J2005-3057 is an r-I star with [Eu/Fe] = +0.94 ± 0.07. J0858-0809 has [Eu/Fe] = +0.23 ± 0.05 and exhibits a carbon abundance corrected for an evolutionary status of [C/Fe]corr = +0.76, thus adding to the small number of known carbon-enhanced r-process stars. All three stars show remarkable agreement with the scaled solar r-process pattern for elements above Ba, consistent with enrichment of the birth gas cloud by a neutron star merger. The abundances for Sr, Y, and Zr, however, deviate from the scaled solar pattern. This indicates that more than one distinct r-process site might be responsible for the observed neutron-capture element abundance pattern. Thorium was detected in J1432-4125 and J2005-3057. Age estimates for J1432-4125 and J2005-3057 were adopted from one of two sets of initial production ratios each by assuming the stars are old. This yielded individual ages of 12 ± 6 Gyr and 10 ± 6 Gyr, respectively. ©2018
MIT Department
Massachusetts Institute of Technology. Department of Physics
MIT Kavli Institute for Astrophysics and Space Research
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DOI of Published Version
https://doi.org/10.3847/1538-4357/AAD37D
