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dc.contributor.authorGallagher, A. J.
dc.contributor.authorLudwig, H. G.
dc.contributor.authorRyan, Sean G.
dc.contributor.authorAoki, W.
dc.date.accessioned2015-08-12T19:48:20Z
dc.date.available2015-08-12T19:48:20Z
dc.date.issued2015-07-31
dc.identifier.citationGallagher , A J , Ludwig , H G , Ryan , S G & Aoki , W 2015 , ' A three-dimensional hydrodynamical line profile analysis of iron lines and barium isotopes in HD140283 ' , Astronomy & Astrophysics , vol. 579 , A94 . https://doi.org/10.1051/0004-6361/201424803
dc.identifier.issn0004-6361
dc.identifier.otherArXiv: http://arxiv.org/abs/1504.02353v1
dc.identifier.otherORCID: /0000-0001-9069-5122/work/30501317
dc.identifier.urihttp://hdl.handle.net/2299/16253
dc.description© 2015 ESO. Reproduced with permission from Astronomy & Astrophysics. Content in the UH Research Archive is made available for personal research, educational, and non-commercial purposes only. Unless otherwise stated, all content is protected by copyright, and in the absence of an open license, permissions for further re-use should be sought from the publisher, the author, or other copyright holder.
dc.description.abstractHeavy-elements, i.e. those beyond the iron peak, mostly form via two neutron capture processes: the s- and r-process. Metal-poor stars should contain fewer isotopes that form via the s-process, according to currently accepted theory. It has been shown in several investigations that theory and observation do not agree well, raising questions on the validity of either the methodology or the theory. We analyse the metal-poor star HD140283, for which we have a high quality spectrum. We test whether a 3D LTE stellar atmosphere and spectrum synthesis code permits a more reliable analysis of the iron abundance and barium isotope ratio than a 1D LTE analysis. Using 3D model atmospheres, we examine 91 iron lines of varying strength and formation depth. This provides us with the star's rotational speed. With this, we model the barium isotope ratio by exploiting the hyperfine structure of the singly ionised 4554 resonance line, and study the impact of the uncertainties in the stellar parameters. HD140283's vsini = 1.65 +/- 0.05 km/s. Barium isotopes under the 3D paradigm show a dominant r-process signature as 77 +/- 6 +/- 17% of barium isotopes form via the r-process, where errors represent the assigned random and systematic errors, respectively. We find that 3D LTE fits reproduce iron line profiles better than those in 1D, but do not provide a unique abundance (within the uncertainties). However, we demonstrate that the isotopic ratio is robust against this shortcoming. Our barium isotope result agrees well with currently accepted theory regarding the formation of the heavy-elements during the early Galaxy. The improved fit to the asymmetric iron line profiles suggests that the current state of 3D LTE modelling provides excellent simulations of fluid flows. However, the abundances they provide are not yet self-consistent. This may improve with NLTE considerations and higher resolution models.en
dc.format.extent16
dc.format.extent2780258
dc.language.isoeng
dc.relation.ispartofAstronomy & Astrophysics
dc.subjectstars: Population II
dc.subjectstars: atmospheres
dc.subjectGalaxy: halo
dc.subjecttechniques: spectroscopic
dc.subjecthydrodynamics
dc.titleA three-dimensional hydrodynamical line profile analysis of iron lines and barium isotopes in HD140283en
dc.contributor.institutionSchool of Physics, Astronomy and Mathematics
dc.contributor.institutionScience & Technology Research Institute
dc.contributor.institutionCentre for Astrophysics Research (CAR)
dc.description.statusPeer reviewed
rioxxterms.versionofrecord10.1051/0004-6361/201424803
rioxxterms.typeJournal Article/Review
herts.preservation.rarelyaccessedtrue


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