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Abundance Analysis of HE 2148–1247, A Star with Extremely Enhanced Neutron Capture Elements

Cohen, Judith G. and Christlieb, Norbert and Qian, Y.-Z. and Wasserburg, G. J. (2003) Abundance Analysis of HE 2148–1247, A Star with Extremely Enhanced Neutron Capture Elements. Astrophysical Journal, 588 (2). pp. 1082-1098. ISSN 0004-637X. doi:10.1086/374269.

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Abundances for 27 elements in the very metal-poor dwarf star HE 2148-1247 are presented, including many of the neutron capture elements. We establish that HE 2148-1247 is a very highly s-process-enhanced star with anomalously high Eu as well, Eu/H ~ half-solar, demonstrating the large addition of heavy nuclei at [Fe/H] = -2.3 dex. Ba and La are enhanced by a somewhat larger factor and reach the solar abundance, while Pb significantly exceeds it, thus demonstrating the addition of substantial s-process material. Ba/Eu is 10 times the solar r-process ratio but much less than that of the s-process, indicating a substantial r-process addition as well. C and N are also very highly enhanced. We have found that HE 2148-1247 is a radial velocity variable; it is probably a small-amplitude long-period binary. The C, N, and the s-process element enhancements were thus presumably produced through mass transfer from a former asymptotic giant branch (AGB) binary companion. The large enhancement of heavy r-nuclides also requires an additional source as this is far above any inventory in the interstellar medium at such low [Fe/H]. We consider that the s-process material was added by mass transfer of a more massive companion during its thermally pulsating AGB phase and ending up as a white dwarf. We further hypothesize that accretion onto the white dwarf from the envelope of the star caused accretion-induced collapse of the white dwarf, forming a neutron star, which then produced heavy r-nuclides and again contaminated its companion. This mechanism in a binary system can thus enhance the envelope of the lower mass star in s- and r-process material sequentially. Through analysis of the neutron capture element abundances taken from the literature for a large sample of very metal-poor stars, we demonstrate, as exemplified by HE 2148-1247, that mass transfer in a suitable binary can be very efficient in enhancing the heavy elements in a star; it appears to be capable of enhancing the s-process elements in very metal-poor stars to near the solar abundance but not substantially above it. The yield of Pb relative to Ba appears to vary among very metal-poor stars.

Item Type:Article
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URLURL TypeDescription Paper
Cohen, Judith G.0000-0002-8039-4673
Christlieb, Norbert0000-0002-4043-2727
Wasserburg, G. J.0000-0002-7957-8029
Additional Information:© 2003 American Astronomical Society. Received 2002 November 22; accepted 2002 December 30. Based on observations obtained at the W. M. Keck Observatory, which is operated jointly by the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The entire Keck/HIRES user community owes a huge debt to Jerry Nelson, Gerry Smith, Steve Vogt, and many other people who have worked to make the Keck Telescope and HIRES a reality and to operate and maintain the Keck Observatory. We are grateful to the W. M. Keck Foundation for the vision to fund the construction of the W. M. Keck Observatory. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. We thank C. Conselice and I. Ivans for acquiring the direct images used for photometry and A. McWilliam for providing a code to calculate hfs. J. G. C. is grateful for partial support from NSF grants AST-9819614 and AST-0205951. N. C. acknowledges financial support through a Marie Curie Fellowship of the European Community program Improving Human Research Potential and the Socio-Economic Knowledge under contract number HPMFCT-2002-01437, and from Deutsche Forschungsgemeinschaft under grant Re 353/44-1. Y. Z. Q. is supported by DOE grants DE-FG02-87ER40328 and DE-FG02-00ER41149, and G. J. W. by NASA grant NAG5-11725.
Funding AgencyGrant Number
W. M. Keck FoundationUNSPECIFIED
Marie Curie FellowshipHPMF-CT-2002-01437
Deutsche Forschungsgemeinschaft (DFG)Re 353/44-1
Department of Energy (DOE)DE-FG02-87ER40328
Department of Energy (DOE)DE-FG02-00ER41149
Subject Keywords:stars: abundances; stars: chemically peculiar; stars: evolution; stars: Population II
Issue or Number:2
Record Number:CaltechAUTHORS:20131210-145233709
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Official Citation:Abundance Analysis of HE 2148–1247, A Star with Extremely Enhanced Neutron Capture Elements Judith G. Cohen et al. 2003 ApJ 588 1082
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:42937
Deposited By: Ruth Sustaita
Deposited On:10 Dec 2013 23:44
Last Modified:10 Nov 2021 16:30

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