{
  "id": "1906.08281",
  "version": "v1",
  "published": "2019-06-19T18:04:02.000Z",
  "updated": "2019-06-19T18:04:02.000Z",
  "title": "Non-LTE analysis of K I in late-type stars",
  "authors": [
    "Henrique Reggiani",
    "Anish M. Amarsi",
    "Karin Lind",
    "Paul S. Barklem",
    "Oleg Zatsarinny",
    "Klaus Bartschat",
    "Dmitry V. Fursa",
    "Igor Bray",
    "Lorenzo Spina",
    "Jorge Meléndez"
  ],
  "comment": "18 pages, 15 Figures",
  "categories": [
    "astro-ph.SR"
  ],
  "abstract": "Older GCE models predict [K/Fe] ratios as much as 1 dex lower than those inferred from stellar observations. Abundances of potassium are mainly based on analyses of the 7698 $\\AA$ resonance line, and the discrepancy between models and observations is in part caused by the LTE assumption. We study the statistical equilibrium of KI, focusing on the non-LTE effects on the $7698 \\ \\AA$ line. We aim to determine how non-LTE abundances of K can improve the analysis of its chemical evolution, and help to constrain the yields of models. We construct a model atom that employs the most up-to-date data. In particular, we calculate and present inelastic e+K collisional excitation cross-sections from the convergent close-coupling and the $B$-Spline $R$-matrix methods, and H+K collisions from the two-electron model. We constructed a fine grid of non-LTE abundance corrections that span $4000<\\teff / \\rm{K}<8000$, $0.50<\\lgg<5.00$, $-5.00<\\feh<+0.50$, and applied the corrections to abundances from the literature. In concordance with previous studies, we find severe non-LTE effects in the $7698 \\ \\AA$ line, which is stronger in non-LTE with abundance corrections that can reach $\\sim-0.7\\,\\dex$. We explore the effects of atmospheric inhomogeneity by computing a full 3D non-LTE stellar spectrum of KI for a test star. We find that 3D is necessary to predict a correct shape of the resonance 7698 $\\AA$ line, but the line strength is similar to that found in 1D non-LTE. Our non-LTE abundance corrections reduce the scatter and change the cosmic trends of literature K abundances. In the regime [Fe/H]$\\lesssim-1.0$ the non-LTE abundances show a good agreement with the GCE model with yields from rotating massive stars. The reduced scatter of the non-LTE corrected abundances of a sample of solar twins shows that line-by-line differential analysis techniques cannot fully compensate for systematic modelling errors.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2019-06-19T18:04:02.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "late-type stars",
      "non-lte analysis",
      "full 3d non-lte stellar spectrum",
      "non-lte abundance corrections reduce",
      "older gce models predict"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 18,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}