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 - Publisher Copyright:
© 2019. The American Astronomical Society. All rights reserved.
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 - http://www.scopus.com/inward/record.url?scp=85064468306&partnerID=8YFLogxK
U2 - 10.3847/1538-4357/ab0c02
DO - 10.3847/1538-4357/ab0c02
M3 - Article
SN - 0004-637X
VL - 874
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 148
ER -