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CS29497-030 Abundance Constraints on Neutron-Capture Nucleosynthesis

Published online by Cambridge University Press:  23 December 2005

Inese I. Ivans
Affiliation:
Dept. of Astronomy, California Institute of Technology, Pasadena, CA 91125, USA email: iii@astro.caltech.edu
Chris Sneden
Affiliation:
Dept. of Astronomy, University of Texas, Austin, TX 78712, USA
Roberto Gallino
Affiliation:
Dipartimento di Fisica Generale, Universita' di Torino, 10125 Torino, Italy
John J. Cowan
Affiliation:
Dept. of Physics and Astronomy, University of Oklahoma, Norman, OK 73019, USA
George W. Preston
Affiliation:
Observatories of the Carnegie Institution of Washington, Pasadena, CA 91101, USA
Sara Bisterzo
Affiliation:
Dipartimento di Fisica Generale, Universita' di Torino, 10125 Torino, Italy
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Abstract

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Chemical abundances and upper limits of three dozen elements have been derived for the binary blue metal-poor, extremely lead-rich star CS29497-030. The findings include a large contribution of s-process material (e.g., [Pb/Fe] >3.5) and a large contribution of r-process material (e.g, [Eu/Fe] ∼2), abundances which place it in the class of objects known as r+s stars. The ratio of [Zr/Nb] ∼0, along with its stellar parameters, indicates that it is not an intrinsic AGB star. Modelling the abundance distribution (which includes the first Bi abundance determination for any metal-poor star) with s-process calculations employing FRANEC models, there is excellent agreement with the observations by adopting a 1.3 M[odot ] AGB model with an enhanced 13C-pocket and a pre-enrichment of r-process material. In this scenario, the initial abundances of CS29497-030 and its binary partner arose from a parent cloud with an extreme r-process abundance, in which star formation was triggered by a core-collapse supernova which polluted, snowplowed, and clumped a nearby molecular cloud. Pollution from the former AGB star's dredged-up material subsequently enriched the envelope composition of CS29497-030 (Ivans et al. 2005). Critical tests of this model and scenario include the dependence of abundance ratios on systematics due to non-LTE effects, the choice of stellar parameters and model atmospheres, and the assumed abundance pattern of the protostellar cloud out of which the CS29497-030 binary system formed.

Type
Contributed Papers
Copyright
© 2005 International Astronomical Union