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Abundances of Sr, Y, and Zr in metal-poor stars and implications for chemical evolution in the early galaxy

Qian, Y.-Z. and Wasserburg, G. J. (2008) Abundances of Sr, Y, and Zr in metal-poor stars and implications for chemical evolution in the early galaxy. Astrophysical Journal, 687 (1). pp. 272-286. ISSN 0004-637X. doi:10.1086/591545.

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We have attributed the elements from Sr through Ag in stars of low metallicities ([Fe/H] ≾ -1.5) to charged-particle reactions (CPRs) in neutrino-driven winds, which are associated with neutron star formation in low-mass and normal supernovae (SNe) from progenitors of ~8-11 M⊙ and ~12-25 M⊙, respectively. Using this rule and attributing all Fe production to normal SNe, we previously developed a phenomenological two-component model, which predicts that [Sr/Fe] ≥ -0.32 for all metal-poor stars. This is in direct conflict with the high-resolution data now available, which show that there is a great shortfall of Sr relative to Fe in many stars with [Fe/H] ≾3. The same conflict also exists for the CPR elements Y and Zr. We show that the data require a stellar source leaving behind black holes and that hypernovae (HNe) from progenitors of ~25-50 M⊙ are the most plausible candidates. If we expand our previous model to include three components (low-mass and normal SNe and HNe), we find that essentially all of the data are very well described by the new model. The HN yield pattern for the low-A elements from Na through Zn ( including Fe) is inferred from the stars deficient in Sr, Y, and Zr. We estimate that HNe contributed ~24% of the bulk solar Fe inventory while normal SNe contributed only ~ 9% (not the usually assumed ~33%). This implies a greatly reduced role of normal SNe in the chemical evolution of the low-A elements.

Item Type:Article
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Wasserburg, G. J.0000-0002-7957-8029
Additional Information:© 2008 The American Astronomical Society. Received 2008 February 28; accepted 2008 July 2. We thank an anonymous reviewer for criticism and suggestions that greatly improved the paper. This work was supported in part by DOE grants DE-FG02-87ER40328 (Y. Z. Q.) and DE-FG03- 88ER13851 (G. J. W.), Caltech Division Contribution 9004 (1125). G. J. W. acknowledges NASA’s Cosmochemistry Program for research support provided through J. Nuth at the Goddard Space Flight Center. He also appreciates the generosity of the Epsilon Foundation.
Funding AgencyGrant Number
Department of EnergyDE-FG02-87ER40328
Department of EnergyDE-FG0388ER13851
Epsilon FoundationUNSPECIFIED
Subject Keywords:nuclear reactions; nucleosynthesis; abundances; stars: abundances; stars: Population II; supernovae: general
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Other Numbering System NameOther Numbering System ID
Caltech Division of Geological and Planetary Sciences9004
Lunatic Asylum Lab1125
Issue or Number:1
Record Number:CaltechAUTHORS:QIAapj08
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13533
Deposited By: Tony Diaz
Deposited On:14 Aug 2009 15:35
Last Modified:08 Nov 2021 22:38

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