The R-process alliance: chemical abundances for a trio of r-process-enhanced stars-one strong, one moderate, and one mild

Madelyn Cain; Anna Frebel; Maude Gull; Alexander P. Ji; Vinicius M. Placco; Timothy C. Beers; Jorge Meléndez; Rana Ezzeddine; Andrew R. Casey; Terese T. Hansen; Ian U. Roederer; Charli Sakari

doi:10.3847/1538-4357/aad37d

The R-process alliance: chemical abundances for a trio of r-process-enhanced stars-one strong, one moderate, and one mild

Madelyn Cain, Anna Frebel, Maude Gull, Alexander P. Ji, Vinicius M. Placco, Timothy C. Beers, Jorge Meléndez, Rana Ezzeddine, Andrew R. Casey, Terese T. Hansen, Ian U. Roederer, Charli Sakari

School of Physics and Astronomy

Research output: Contribution to journal › Article › Research › peer-review

23 Citations (Scopus)

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.

Original language	English
Article number	43
Number of pages	12
Journal	The Astrophysical Journal
Volume	864
Issue number	1
DOIs	https://doi.org/10.3847/1538-4357/aad37d
Publication status	Published - 1 Sept 2018

Keywords

Galaxy: halo
nuclear reactions
nucleosynthesis, abundance
stars: Abundances
stars: Population II Supporting material: machine-readable table

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Cain, M., Frebel, A., Gull, M., Ji, A. P., Placco, V. M., Beers, T. C., Meléndez, J., Ezzeddine, R., Casey, A. R., Hansen, T. T., Roederer, I. U., & Sakari, C. (2018). The R-process alliance: chemical abundances for a trio of r-process-enhanced stars-one strong, one moderate, and one mild. The Astrophysical Journal, 864(1), Article 43. https://doi.org/10.3847/1538-4357/aad37d

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title = "The R-process alliance: chemical abundances for a trio of r-process-enhanced stars-one strong, one moderate, and one mild",

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.",

keywords = "Galaxy: halo, nuclear reactions, nucleosynthesis, abundance, stars: Abundances, stars: Population II Supporting material: machine-readable table",

author = "Madelyn Cain and Anna Frebel and Maude Gull and Ji, {Alexander P.} and Placco, {Vinicius M.} and Beers, {Timothy C.} and Jorge Mel{\'e}ndez and Rana Ezzeddine and Casey, {Andrew R.} and Hansen, {Terese T.} and Roederer, {Ian U.} and Charli Sakari",

year = "2018",

month = sep,

day = "1",

doi = "10.3847/1538-4357/aad37d",

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T1 - The R-process alliance

T2 - chemical abundances for a trio of r-process-enhanced stars-one strong, one moderate, and one mild

AU - Cain, Madelyn

AU - Frebel, Anna

AU - Gull, Maude

AU - Ji, Alexander P.

AU - Placco, Vinicius M.

AU - Beers, Timothy C.

AU - Meléndez, Jorge

AU - Ezzeddine, Rana

AU - Casey, Andrew R.

AU - Hansen, Terese T.

AU - Roederer, Ian U.

AU - Sakari, Charli

PY - 2018/9/1

Y1 - 2018/9/1

N2 - 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.

AB - 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.

KW - Galaxy: halo

KW - nuclear reactions

KW - nucleosynthesis, abundance

KW - stars: Abundances

KW - stars: Population II Supporting material: machine-readable table

UR - http://www.scopus.com/inward/record.url?scp=85053124990&partnerID=8YFLogxK

U2 - 10.3847/1538-4357/aad37d

DO - 10.3847/1538-4357/aad37d

M3 - Article

AN - SCOPUS:85053124990

SN - 0004-637X

VL - 864

JO - The Astrophysical Journal

JF - The Astrophysical Journal

IS - 1

M1 - 43

ER -

The R-process alliance: chemical abundances for a trio of r-process-enhanced stars-one strong, one moderate, and one mild

Abstract

Keywords

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