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25 April 2024 |
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Article overview
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Normal and Outlying Populations of the Milky Way Stellar Halo at [Fe/H] < -2 | | Judith Cohen
; Norbert Christlieb
; Ian Thompson
; Andrew McWilliam
; Stephen Shectman
; Dieter Reimers
; Lutz Wisotzki
; Evan Kirby
; | | Date: |
6 Oct 2013 | | Abstract: | From detailed abundance analysis of >100 Hamburg/ESO candidate extremely
metal-poor (EMP) stars we find 45 with [Fe/H] < -3.0 dex. We identify a
heretofore unidentified group: Ca-deficient stars, with sub-solar [Ca/Fe]
ratios and the lowest neutron-capture abundances; the Ca-deficient group
comprises ~ 10% of the sample, excluding Carbon stars. Our radial velocity
distribution shows that the carbon-enhanced stars with no s-process
enhancements, CEMP-no, and which do not show C2 bands are not preferentially
binary systems. Ignoring Carbon stars, approximately 15% of our sample are
strong (> 5 sigma) outliers in one, or more, elements between Mg and Ni; this
rises to ~19% if very strong (>10 sigma) outliers for Sr and Ba are included.
Examples include: HE0305-0554 with the lowest [Ba/H] known; HE1012-1540 and
HE2323-0256, two (non-velocity variable) C-rich stars with very strong
[Mg,Al/Fe] enhancements; and HE1226-1149 an extremely r-process rich star. | | Source: | arXiv, 1310.1527 | | Services: | Forum | Review | PDF | Favorites | |
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