A new type of extremely metal-poor star

Judith G. Cohen; Andrew McWilliam; Norbert Christlieb; Stephen Shectman; Ian Thompson; Jorge Melendez; Lutz Wisotzki; Dieter Reimers

doi:10.1086/518031

A new type of extremely metal-poor star

Judith G. Cohen^*, Andrew McWilliam, Norbert Christlieb, Stephen Shectman, Ian Thompson, Jorge Melendez, Lutz Wisotzki, Dieter Reimers

^*Corresponding author for this work

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

53 Citations (Scopus)

Abstract

We present an abundance analysis for the extremely metal-poor (EMP) star HE 1424-0241 based on high-dispersion spectra from HIRES at Keck. This star is a giant on the lower red giant branch with [Fe/H] ∼ -4.0 dex. Relative to Fe, HE 1424-0241 has normal Mg, but it shows a very large deficiency of Si, with ε(Si)/ε(Fe) ∼ 1/10 and ε(Si)/ε(Mg) ∼ 1/25 that of all previously known EMP giants or dwarfs. It also has a moderately large deficiency of Ca and a smaller deficit of Ti, combined with enhanced Mn and Co and normal or low C. We suggest that in HE 1424-0241 we see the effect of a very small number of contributing supernovae, and that the SNe II contributing to the chemical inventory of HE 1424-0241 were biased in progenitor mass or in explosion characteristics so as to reproduce its abnormal extremely low Si/Mg ratio. HE 1424-0241 shows a deficiency of the explosive α-burning elements Si, Ca, and Ti coupled with a ratio [Mg/Fe] normal for EMP stars; Mg is produced via hydrostatic α-burning. The latest models of nucleosynthesis in SNe II fail to reproduce the abundance ratios seen in HE 1424-0241 for any combination of the parameter space of core-collapse explosions they explore.

Original language	English
Pages (from-to)	L161-L164
Journal	Astrophysical Journal
Volume	659
Issue number	2 II
DOIs	https://doi.org/10.1086/518031
Publication status	Published - 20 Apr 2007

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title = "A new type of extremely metal-poor star",

abstract = "We present an abundance analysis for the extremely metal-poor (EMP) star HE 1424-0241 based on high-dispersion spectra from HIRES at Keck. This star is a giant on the lower red giant branch with [Fe/H] ∼ -4.0 dex. Relative to Fe, HE 1424-0241 has normal Mg, but it shows a very large deficiency of Si, with ε(Si)/ε(Fe) ∼ 1/10 and ε(Si)/ε(Mg) ∼ 1/25 that of all previously known EMP giants or dwarfs. It also has a moderately large deficiency of Ca and a smaller deficit of Ti, combined with enhanced Mn and Co and normal or low C. We suggest that in HE 1424-0241 we see the effect of a very small number of contributing supernovae, and that the SNe II contributing to the chemical inventory of HE 1424-0241 were biased in progenitor mass or in explosion characteristics so as to reproduce its abnormal extremely low Si/Mg ratio. HE 1424-0241 shows a deficiency of the explosive α-burning elements Si, Ca, and Ti coupled with a ratio [Mg/Fe] normal for EMP stars; Mg is produced via hydrostatic α-burning. The latest models of nucleosynthesis in SNe II fail to reproduce the abundance ratios seen in HE 1424-0241 for any combination of the parameter space of core-collapse explosions they explore.",

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author = "Cohen, {Judith G.} and Andrew McWilliam and Norbert Christlieb and Stephen Shectman and Ian Thompson and Jorge Melendez and Lutz Wisotzki and Dieter Reimers",

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AU - Cohen, Judith G.

AU - McWilliam, Andrew

AU - Christlieb, Norbert

AU - Shectman, Stephen

AU - Thompson, Ian

AU - Melendez, Jorge

AU - Wisotzki, Lutz

AU - Reimers, Dieter

PY - 2007/4/20

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N2 - We present an abundance analysis for the extremely metal-poor (EMP) star HE 1424-0241 based on high-dispersion spectra from HIRES at Keck. This star is a giant on the lower red giant branch with [Fe/H] ∼ -4.0 dex. Relative to Fe, HE 1424-0241 has normal Mg, but it shows a very large deficiency of Si, with ε(Si)/ε(Fe) ∼ 1/10 and ε(Si)/ε(Mg) ∼ 1/25 that of all previously known EMP giants or dwarfs. It also has a moderately large deficiency of Ca and a smaller deficit of Ti, combined with enhanced Mn and Co and normal or low C. We suggest that in HE 1424-0241 we see the effect of a very small number of contributing supernovae, and that the SNe II contributing to the chemical inventory of HE 1424-0241 were biased in progenitor mass or in explosion characteristics so as to reproduce its abnormal extremely low Si/Mg ratio. HE 1424-0241 shows a deficiency of the explosive α-burning elements Si, Ca, and Ti coupled with a ratio [Mg/Fe] normal for EMP stars; Mg is produced via hydrostatic α-burning. The latest models of nucleosynthesis in SNe II fail to reproduce the abundance ratios seen in HE 1424-0241 for any combination of the parameter space of core-collapse explosions they explore.

AB - We present an abundance analysis for the extremely metal-poor (EMP) star HE 1424-0241 based on high-dispersion spectra from HIRES at Keck. This star is a giant on the lower red giant branch with [Fe/H] ∼ -4.0 dex. Relative to Fe, HE 1424-0241 has normal Mg, but it shows a very large deficiency of Si, with ε(Si)/ε(Fe) ∼ 1/10 and ε(Si)/ε(Mg) ∼ 1/25 that of all previously known EMP giants or dwarfs. It also has a moderately large deficiency of Ca and a smaller deficit of Ti, combined with enhanced Mn and Co and normal or low C. We suggest that in HE 1424-0241 we see the effect of a very small number of contributing supernovae, and that the SNe II contributing to the chemical inventory of HE 1424-0241 were biased in progenitor mass or in explosion characteristics so as to reproduce its abnormal extremely low Si/Mg ratio. HE 1424-0241 shows a deficiency of the explosive α-burning elements Si, Ca, and Ti coupled with a ratio [Mg/Fe] normal for EMP stars; Mg is produced via hydrostatic α-burning. The latest models of nucleosynthesis in SNe II fail to reproduce the abundance ratios seen in HE 1424-0241 for any combination of the parameter space of core-collapse explosions they explore.

KW - Nuclear reactions, nucleosynthesis, abundances

KW - Stars: abundances

KW - Supernovae: general

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DO - 10.1086/518031

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SN - 0004-637X

VL - 659

SP - L161-L164

JO - Astrophysical Journal

JF - Astrophysical Journal

IS - 2 II

ER -

A new type of extremely metal-poor star

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