The R-Process Alliance: a comprehensive abundance analysis of HD 222925, a metal-poor star with an extreme R-process enhancement of [Eu/H] = −0.14*
Name
Roederer_2018_ApJ_865_129.pdf
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Checksum (MD5)
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Author(s)
Roederer, Ian U.
Sakari, Charli M.
Placco, Vinicius M.
Beers, Timothy C.
Ezzeddine, Rana
Frebel, Anna
Hansen, Terese T.
Date Issued
October 2018
Journal
Astrophysical journal
Publisher
American Astronomical Society
Citation
Roederer, Ian U., et al., "The R-Process Alliance: a comprehensive abundance analysis of HD 222925, a metal-poor star with an extreme R-process enhancement of [Eu/H] = −0.14*." Astrophysical journal 865, 2 (October 2018): no. 129 doi 10.3847/1538-4357/AADD92 ©2018 Author(s)
Version
Final published version
Abstract
We present a detailed abundance analysis of the bright (V = 9.02), metal-poor ([Fe/H] = -1.47 ± 0.08) field red horizontal-branch star HD 222925, which was observed as part of an ongoing survey by the R-Process Alliance. We calculate stellar parameters and derive abundances for 46 elements based on 901 lines examined in a high-resolution optical spectrum obtained using the Magellan Inamori Kyocera Echelle spectrograph. We detect 28 elements with 38 ≤ Z ≤ 90; their abundance pattern is a close match to the solar r-process component. The distinguishing characteristic of HD 222925 is an extreme enhancement of r-process elements ([Eu/Fe] = +1.33 ± 0.08, [Ba/Eu] = -0.78 ± 0.10) in a moderately metal-poor star, so the abundance of r-process elements is the highest ([Eu/H] = -0.14 ± 0.09) in any known r-process-enhanced star. The abundance ratios among lighter (Z ≤ 30) elements are typical for metal-poor stars, indicating that production of these elements was dominated by normal Type II supernovae, with no discernible contributions from Type Ia supernovae or asymptotic giant branch stars. The chemical and kinematic properties of HD 222925 suggest it formed in a low-mass dwarf galaxy, which was enriched by a high-yield r-process event before being disrupted by interaction with the Milky Way. ©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/AADD92
