The R-Process Alliance: discovery of a low-α, r-process-enhanced metal-poor star in the galactic halo

Charli M. Sakari; Ian U. Roederer; Vinicius M. Placco; Timothy C. Beers; Rana Ezzeddine; Anna Frebel; Terese Hansen; Christopher Sneden; John J. Cowan; George Wallerstein; Elizabeth M. Farrell; Kim A. Venn; Gal Matijevič; Rosemary F. G. Wyse; Joss Bland-Hawthorn; Cristina Chiappini; Kenneth C. Freeman; Brad K. Gibson; Eva K. Grebel; Amina Helmi; Georges Kordopatis; Andrea Kunder; Julio Navarro; Warren Reid; George Seabroke; Matthias Steinmetz; Fred Watson

doi:10.3847/1538-4357/ab0c02

The R-Process Alliance: discovery of a low-α, r-process-enhanced metal-poor star in the galactic halo

Charli M. Sakari, Ian U. Roederer, Vinicius M. Placco, Timothy C. Beers, Rana Ezzeddine, Anna Frebel, Terese Hansen, Christopher Sneden, John J. Cowan, George Wallerstein, Elizabeth M. Farrell, Kim A. Venn, Gal Matijevič, Rosemary F. G. Wyse, Joss Bland-Hawthorn, Cristina Chiappini, Kenneth C. Freeman, Brad K. Gibson, Eva K. Grebel, Amina HelmiGeorges Kordopatis, Andrea Kunder, Julio Navarro, Warren Reid, George Seabroke, Matthias Steinmetz, Fred Watson

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Abstract

A new moderately r-process-enhanced metal-poor star, RAVE J093730.5-062655, has been identified in the Milky Way halo as part of an ongoing survey by the R-Process Alliance. The temperature and surface gravity indicate that J0937-0626 is likely a horizontal branch star. At [Fe/H] = -1.86, J0937-0626 is found to have subsolar [X/Fe] ratios for nearly every light, α, and Fe-peak element. The low [α/Fe] ratios can be explained by an ∼0.6 dex excess of Fe; J0937-0626 is therefore similar to the subclass of "iron-enhanced" metal-poor stars. A comparison with Milky Way field stars at [Fe/H] = -2.5 suggests that J0937-0626 was enriched in material from an event, possibly a Type Ia supernova, that created a significant amount of Cr, Mn, Fe, and Ni and smaller amounts of Ca, Sc, Ti, and Zn. The r-process enhancement of J0937-0626 is likely due to a separate event, which suggests that its birth environment was highly enriched in r-process elements. The kinematics of J0937-0626, based on Gaia DR2 data, indicate a retrograde orbit in the Milky Way halo; J0937-0626 was therefore likely accreted from a dwarf galaxy that had significant r-process enrichment.

Original language	English
Article number	148
Pages (from-to)	1-13
Number of pages	13
Journal	The Astrophysical Journal
Volume	874
Issue number	2
DOIs	https://doi.org/10.3847/1538-4357/ab0c02
Publication status	Published - 1 Apr 2019

Bibliographical note

Copyright 2019 The American Astronomical Society. First published in the Astrophysical Journal, 874(2), 148, 2019, published by IOP Publishing. The original publication is available at http://www.doi.org/10.3847/1538-4357/ab0c02. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

Keywords

Galaxy: formation
stars: abundances
stars: atmospheres
stars: fundamental parameters
stars: individual (RAVE J093730.5-062655)

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10.3847/1538-4357/ab0c02

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Sakari, C. M., Roederer, I. U., Placco, V. M., Beers, T. C., Ezzeddine, R., Frebel, A., Hansen, T., Sneden, C., Cowan, J. J., Wallerstein, G., Farrell, E. M., Venn, K. A., Matijevič, G., Wyse, R. F. G., Bland-Hawthorn, J., Chiappini, C., Freeman, K. C., Gibson, B. K., Grebel, E. K., ... Watson, F. (2019). The R-Process Alliance: discovery of a low-α, r-process-enhanced metal-poor star in the galactic halo. The Astrophysical Journal, 874(2), 1-13. Article 148. https://doi.org/10.3847/1538-4357/ab0c02

@article{31cf7b7f1d824a86885357e1e44ccb1a,

title = "The R-Process Alliance: discovery of a low-α, r-process-enhanced metal-poor star in the galactic halo",

abstract = "A new moderately r-process-enhanced metal-poor star, RAVE J093730.5-062655, has been identified in the Milky Way halo as part of an ongoing survey by the R-Process Alliance. The temperature and surface gravity indicate that J0937-0626 is likely a horizontal branch star. At [Fe/H] = -1.86, J0937-0626 is found to have subsolar [X/Fe] ratios for nearly every light, α, and Fe-peak element. The low [α/Fe] ratios can be explained by an ∼0.6 dex excess of Fe; J0937-0626 is therefore similar to the subclass of {"}iron-enhanced{"} metal-poor stars. A comparison with Milky Way field stars at [Fe/H] = -2.5 suggests that J0937-0626 was enriched in material from an event, possibly a Type Ia supernova, that created a significant amount of Cr, Mn, Fe, and Ni and smaller amounts of Ca, Sc, Ti, and Zn. The r-process enhancement of J0937-0626 is likely due to a separate event, which suggests that its birth environment was highly enriched in r-process elements. The kinematics of J0937-0626, based on Gaia DR2 data, indicate a retrograde orbit in the Milky Way halo; J0937-0626 was therefore likely accreted from a dwarf galaxy that had significant r-process enrichment.",

keywords = "Galaxy: formation, stars: abundances, stars: atmospheres, stars: fundamental parameters, stars: individual (RAVE J093730.5-062655)",

author = "Sakari, \{Charli M.\} and Roederer, \{Ian U.\} and Placco, \{Vinicius M.\} and Beers, \{Timothy C.\} and Rana Ezzeddine and Anna Frebel and Terese Hansen and Christopher Sneden and Cowan, \{John J.\} and George Wallerstein and Farrell, \{Elizabeth M.\} and Venn, \{Kim A.\} and Gal Matijevi{\v c} and Wyse, \{Rosemary F. G.\} and Joss Bland-Hawthorn and Cristina Chiappini and Freeman, \{Kenneth C.\} and Gibson, \{Brad K.\} and Grebel, \{Eva K.\} and Amina Helmi and Georges Kordopatis and Andrea Kunder and Julio Navarro and Warren Reid and George Seabroke and Matthias Steinmetz and Fred Watson",

note = "Copyright 2019 The American Astronomical Society. First published in the Astrophysical Journal, 874(2), 148, 2019, published by IOP Publishing. The original publication is available at http://www.doi.org/10.3847/1538-4357/ab0c02. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.",

year = "2019",

month = apr,

day = "1",

doi = "10.3847/1538-4357/ab0c02",

language = "English",

volume = "874",

pages = "1--13",

journal = "The Astrophysical Journal",

issn = "0004-637X",

publisher = "American Astronomical Society",

number = "2",

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Sakari, CM, Roederer, IU, Placco, VM, Beers, TC, Ezzeddine, R, Frebel, A, Hansen, T, Sneden, C, Cowan, JJ, Wallerstein, G, Farrell, EM, Venn, KA, Matijevič, G, Wyse, RFG, Bland-Hawthorn, J, Chiappini, C, Freeman, KC, Gibson, BK, Grebel, EK, Helmi, A, Kordopatis, G, Kunder, A, Navarro, J, Reid, W, Seabroke, G, Steinmetz, M & Watson, F 2019, 'The R-Process Alliance: discovery of a low-α, r-process-enhanced metal-poor star in the galactic halo', The Astrophysical Journal, vol. 874, no. 2, 148, pp. 1-13. https://doi.org/10.3847/1538-4357/ab0c02

TY - JOUR

T1 - The R-Process Alliance

T2 - discovery of a low-α, r-process-enhanced metal-poor star in the galactic halo

AU - Sakari, Charli M.

AU - Roederer, Ian U.

AU - Placco, Vinicius M.

AU - Beers, Timothy C.

AU - Ezzeddine, Rana

AU - Frebel, Anna

AU - Hansen, Terese

AU - Sneden, Christopher

AU - Cowan, John J.

AU - Wallerstein, George

AU - Farrell, Elizabeth M.

AU - Venn, Kim A.

AU - Matijevič, Gal

AU - Wyse, Rosemary F. G.

AU - Bland-Hawthorn, Joss

AU - Chiappini, Cristina

AU - Freeman, Kenneth C.

AU - Gibson, Brad K.

AU - Grebel, Eva K.

AU - Helmi, Amina

AU - Kordopatis, Georges

AU - Kunder, Andrea

AU - Navarro, Julio

AU - Reid, Warren

AU - Seabroke, George

AU - Steinmetz, Matthias

AU - Watson, Fred

N1 - Copyright 2019 The American Astronomical Society. First published in the Astrophysical Journal, 874(2), 148, 2019, published by IOP Publishing. The original publication is available at http://www.doi.org/10.3847/1538-4357/ab0c02. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

PY - 2019/4/1

Y1 - 2019/4/1

N2 - A new moderately r-process-enhanced metal-poor star, RAVE J093730.5-062655, has been identified in the Milky Way halo as part of an ongoing survey by the R-Process Alliance. The temperature and surface gravity indicate that J0937-0626 is likely a horizontal branch star. At [Fe/H] = -1.86, J0937-0626 is found to have subsolar [X/Fe] ratios for nearly every light, α, and Fe-peak element. The low [α/Fe] ratios can be explained by an ∼0.6 dex excess of Fe; J0937-0626 is therefore similar to the subclass of "iron-enhanced" metal-poor stars. A comparison with Milky Way field stars at [Fe/H] = -2.5 suggests that J0937-0626 was enriched in material from an event, possibly a Type Ia supernova, that created a significant amount of Cr, Mn, Fe, and Ni and smaller amounts of Ca, Sc, Ti, and Zn. The r-process enhancement of J0937-0626 is likely due to a separate event, which suggests that its birth environment was highly enriched in r-process elements. The kinematics of J0937-0626, based on Gaia DR2 data, indicate a retrograde orbit in the Milky Way halo; J0937-0626 was therefore likely accreted from a dwarf galaxy that had significant r-process enrichment.

AB - A new moderately r-process-enhanced metal-poor star, RAVE J093730.5-062655, has been identified in the Milky Way halo as part of an ongoing survey by the R-Process Alliance. The temperature and surface gravity indicate that J0937-0626 is likely a horizontal branch star. At [Fe/H] = -1.86, J0937-0626 is found to have subsolar [X/Fe] ratios for nearly every light, α, and Fe-peak element. The low [α/Fe] ratios can be explained by an ∼0.6 dex excess of Fe; J0937-0626 is therefore similar to the subclass of "iron-enhanced" metal-poor stars. A comparison with Milky Way field stars at [Fe/H] = -2.5 suggests that J0937-0626 was enriched in material from an event, possibly a Type Ia supernova, that created a significant amount of Cr, Mn, Fe, and Ni and smaller amounts of Ca, Sc, Ti, and Zn. The r-process enhancement of J0937-0626 is likely due to a separate event, which suggests that its birth environment was highly enriched in r-process elements. The kinematics of J0937-0626, based on Gaia DR2 data, indicate a retrograde orbit in the Milky Way halo; J0937-0626 was therefore likely accreted from a dwarf galaxy that had significant r-process enrichment.

KW - Galaxy: formation

KW - stars: abundances

KW - stars: atmospheres

KW - stars: fundamental parameters

KW - stars: individual (RAVE J093730.5-062655)

UR - https://www.scopus.com/pages/publications/85064468306

U2 - 10.3847/1538-4357/ab0c02

DO - 10.3847/1538-4357/ab0c02

M3 - Article

AN - SCOPUS:85064468306

SN - 0004-637X

VL - 874

SP - 1

EP - 13

JO - The Astrophysical Journal

JF - The Astrophysical Journal

IS - 2

M1 - 148

ER -

The R-Process Alliance: discovery of a low-α, r-process-enhanced metal-poor star in the galactic halo

Abstract

Bibliographical note

Keywords

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