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dc.contributor.authorGallagher, A.J.
dc.contributor.authorRyan, Sean G.
dc.contributor.authorGarcia Perez, A.E.
dc.contributor.authorAoki, W.
dc.date.accessioned2012-11-29T11:59:51Z
dc.date.available2012-11-29T11:59:51Z
dc.date.issued2010
dc.identifier.citationGallagher , A J , Ryan , S G , Garcia Perez , A E & Aoki , W 2010 , ' The barium isotopic mixture for the metal-poor subgiant star HD 140283 ' , Astronomy and Astrophysics , vol. 523 , 24 . https://doi.org/10.1051/0004-6361/201014970
dc.identifier.issn0004-6361
dc.identifier.otherPURE: 137400
dc.identifier.otherPURE UUID: 918f0714-d3fb-49f7-868e-74c60b4430e0
dc.identifier.otherdspace: 2299/5153
dc.identifier.otherScopus: 77950245125
dc.identifier.urihttp://hdl.handle.net/2299/9253
dc.descriptionOriginal article can be found at: http://www.aanda.org Copyright European Southern Observatory
dc.description.abstractContext: Current theory regarding heavy element nucleosynthesis in metal-poor environments states that the r-process would be dominant. The star HD 140283 has been the subject of debate after it appeared in some studies to be dominated by the s-process. Aims: We provide an independent measure of the Ba isotope mixture using an extremely high quality spectrum and an extensive χ2 analysis. Methods: We have acquired a very high resolution (R ≡ λ/Δλ = 95000), very high signal-to-noise (S / N = 1110 around 4554 Å, as calculated in IRAF) spectrum of HD 140283. We exploit hyperfine splitting of the Ba ii 4554 Å and 4934 Å resonance lines in an effort to constrain the isotope ratio in 1D LTE. Using the code ATLAS in conjunction with KURUCZ06 model atmospheres we analyse 93 Fe lines to determine the star’s macroturbulence. With this information we construct a grid of Ba synthetic spectra and, using a χ2 code, fit these to our observed data to determine the isotopic ratio, fodd, which represents the ratio of odd to even isotopes. The odd isotopes and 138Ba are synthesized by the r- and s-process while the other even isotopes (134,136Ba) are synthesized purely by the s-process. We also analyse the Eu lines. Results: We set a new upper limit of the rotation of HD 140283 at vsini ≤ 3.9 kms-1, a new upper limit on [Eu/H] < −2.80 and abundances [Fe/H] = −2.59 ± 0.09, [Ba/H] = −3.46 ± 0.11. This leads to a new lower limit on [Ba/Eu] > −0.66. We find that, in the framework of a 1D LTE analysis, the isotopic ratios of Ba in HD 140283 indicate fodd = 0.02 ± 0.06, a purely s-process signature. This implies that observations and analysis do not validate currently accepted theory. Conclusions: We speculate that a 1D code, due to simplifying assumptions, is not adequate when dealing with observations with high levels of resolution and signal-to-noise because of the turbulent motions associated with a 3D stellar atmosphere. New approaches to analysing isotopic ratios, in particular 3D hydrodynamics, need to be considered when dealing with the levels of detail required to properly determine them. However published 3D results exacerbate the disagreement between theory and observation.en
dc.format.extent15
dc.language.isoeng
dc.relation.ispartofAstronomy and Astrophysics
dc.rightsOpen
dc.subjectStars
dc.subjectgalaxy
dc.subjectnuclear reactions
dc.subjectnucleosynthesis
dc.subjectabundances
dc.titleThe barium isotopic mixture for the metal-poor subgiant star HD 140283en
dc.contributor.institutionSchool of Physics, Astronomy and Mathematics
dc.contributor.institutionScience & Technology Research Institute
dc.contributor.institutionCentre for Astrophysics Research
dc.description.statusPeer reviewed
dc.identifier.urlhttp://www.scopus.com/inward/record.url?scp=77950245125&partnerID=8YFLogxK
dc.relation.schoolSchool of Physics, Astronomy and Mathematics
dc.description.versiontypeFinal Accepted Version
dcterms.dateAccepted2010
rioxxterms.versionAM
rioxxterms.versionofrecordhttps://doi.org/10.1051/0004-6361/201014970
rioxxterms.typeJournal Article/Review
herts.preservation.rarelyaccessedtrue
herts.rights.accesstypeOpen


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