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Stellar abundances in the early galaxy and two r-process components

Qian, Y.-Z. and Wasserburg, G. J. (2000) Stellar abundances in the early galaxy and two r-process components. Physics Reports, 333-334 . pp. 77-108. ISSN 0370-1573. doi:10.1016/S0370-1573(00)00017-X.

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We present quantitative predictions for the abundances of r-process elements in stars formed very early in the Galactic history using a phenomenological two-component r-process model based on the ^(129)I and ^(182)Hf inventory in the early solar system. This model assumes that a standard mass of the ISM dilutes the debris from an individual supernova. High-frequency supernova H events and low-frequency supernova L events are proposed in the model with characteristics determined by the meteoritic data on ^(129)I and ^(182)Hf. The yields in an H or L event are obtained from these characteristics and the solar r-process abundances under the assumption that the yield template for the high-mass (A>130) nuclei associated with ^(182)W or the low-mass (A≤130) nuclei associated with ^(127)I is the same for both the H and L events and follows the corresponding solar r-pattern in each mass region. This choice of the yield templates is justified by the regular solar-like r-process abundance pattern for Ba and higher atomic numbers observed in very metal-poor stars. The abundance of Eu, not Fe, is proposed as a key guide to the age of very metal-poor stars. We predict that stars with log ε(Eu) = - 2.98 to −2.22 were formed from an ISM contaminated most likely by a single H event within the first ~ 10^7 yr of the Galactic history and should have an Ag/Eu abundance ratio less than the corresponding solar r-process value by a factor of at least 10. Many of the very metal-poor stars observed so far are considered here to have been formed from an ISM contaminated by many (∼10) r-process events. Stars formed from an ISM contaminated only by a pure L event would have an Ag/Eu ratio higher than the corresponding solar r-process value but would be difficult to find due to the low-frequency of the L events. However, variations in the relative abundances of the low- and high-mass regions should be detectable in very metal-poor stars.

Item Type:Article
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URLURL TypeDescription Paper
Wasserburg, G. J.0000-0002-7957-8029
Additional Information:© 2000 Elsevier Science B.V. This work is dedicated to David Norman Schramm and is in the spirit of excitement, hypotheses, and observation that typified his approach. One of us remembers participating in the early wonders of nuclear cosmochronology and the search for extinct nuclei during his thesis. The other remembers the dense presentations and mysteries of earlier nuclear cosmochronologic reports and the interest and excitement of the new studies. The approach used here seeks to follow that of previous scholars. "The true method of experience first lights the candle (by hypothesis), and then by means of the candle shows the way, commencing as it does with experience duly ordered ... and from it educing axioms ('first fruits', provisional conclusions), and from established axioms again new experiments ... Experiment itself shall judge". - Francis Bacon, Novum Organum (1620). We greatly appreciate the support by John Cowan and Christopher Sneden in freely providing us information on their work and in maintaining a continued level of interest in testing alternative models, however speculative. Discussions with Andrew McWilliam on abundances in very metalpoor stars were of considerable aid. We thank Petr Vogel for comments on an earlier draft of the paper. This work was supported in part by the US Department of Energy under contract W-7405-ENG-36 and grant DE-FG03-88ER-13851, and by NASA under grant NAG 5-4076, Caltech Division Contribution No. 8641(1032). Y.-Z.Q. was supported by the J. Robert Oppenheimer Fellowship at Los Alamos National Laboratory.
Funding AgencyGrant Number
Department of Energy (DOE)W-7405-ENG-36
Department of Energy (DOE)DE-FG03-88ER13851
Los Alamos National Laboratory J. Robert Oppenheimer FellowshipUNSPECIFIED
Subject Keywords:r-process nucleosynthesis; Abundances in metal-poor stars; Galactic chemical evolution
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Caltech Division of Geological and Planetary Sciences8641
Lunatic Asylum Lab1032
Classification Code:PACS: 26.30.+k; 97.10.Tk; 97.20.Tr; 98.35.Bd
Record Number:CaltechAUTHORS:20131120-074209032
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Official Citation:Y.-Z. Qian, G.J. Wasserburg, Stellar abundances in the early galaxy and two r-process components, Physics Reports, Volumes 333–334, August 2000, Pages 77-108, ISSN 0370-1573, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:42582
Deposited By: Ruth Sustaita
Deposited On:20 Nov 2013 20:52
Last Modified:10 Nov 2021 16:25

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