Non-LTE line formation of Fe in late-type stars - III. 3D non-LTE analysis of metal-poor stars

Publication: Research - peer-reviewJournal article

DOI

  • A. M. Amarsi
    A. M. AmarsiAustralian Natl Univ, Australian National University, Res Sch Astron & Astrophys
  • K. Lind
    K. LindMax Planck Inst Astron, Max Planck SocietyUppsala Univ, Uppsala University, Dept Phys & Astron, Theoret Astrophys
  • M. Asplund
    M. AsplundAustralian Natl Univ, Australian National University, Res Sch Astron & Astrophys
  • P. S. Barklem
    P. S. BarklemUppsala Univ, Uppsala University, Dept Phys & Astron, Theoret Astrophys
  • R. Collet

As one of the most important elements in astronomy, iron abundance determinations need to be as accurate as possible. We investigate the accuracy of spectroscopic iron abundance analyses using archetypal metal-poor stars. We perform detailed 3D non-LTE radiative transfer calculations based on 3D hydrodynamic STAGGER model atmospheres, and employ a new model atom that includes new quantum-mechanical neutral hydrogen collisional rate coefficients. With the exception of the red giant HD122563, we find that the 3D non-LTE models achieve Fe I/Fe II excitation and ionization balance as well as not having any trends with equivalent width to within modelling uncertainties of 0.05 dex, all without having to invoke any microturbulent broadening; for HD122563 we predict that the current best parallax-based surface gravity is overestimated by 0.5 dex. Using a 3D non-LTE analysis, we infer iron abundances from the 3D model atmospheres that are roughly 0.1 dex higher than corresponding abundances from 1D MARCS model atmospheres; these differences go in the same direction as the non-LTE effects themselves. We make available grids of departure coefficients, equivalent widths and abundance corrections, calculated on 1D MARCS model atmospheres and horizontally and temporally averaged 3D STAGGER model atmospheres.

Original languageEnglish
JournalMonthly Notices of the Royal Astronomical Society
Volume463
Issue number2
Pages (from-to)1518-1533
Number of pages16
ISSN0035-8711
DOIs
StatePublished - 1 Dec 2016

    Keywords

  • line: formation, radiative transfer, methods: numerical, stars: abundances, stars: atmospheres, RELATIVE OSCILLATOR-STRENGTHS, GALACTIC CHEMICAL EVOLUTION, NEUTRAL HYDROGEN COLLISIONS, RADIATIVE-TRANSFER CODE, ATOM-ATOM COLLISIONS, COOL DWARF STARS, R-MATRIX METHOD, STELLAR ATMOSPHERES, MODEL ATMOSPHERES, CROSS-SECTIONS

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ID: 107707260