{
  "id": "1902.04897",
  "version": "v1",
  "published": "2019-02-13T13:31:02.000Z",
  "updated": "2019-02-13T13:31:02.000Z",
  "title": "Spectral analysis of the barium central star of the planetary nebula Hen 2-39",
  "authors": [
    "L. Löbling",
    "H. M. J. Boffin",
    "D. Jones"
  ],
  "comment": "26 pages, 18 figures",
  "categories": [
    "astro-ph.SR"
  ],
  "abstract": "Barium stars are peculiar red giants characterized by an overabundance of s-process elements along with an enrichment in carbon. These stars are discovered in binaries with white dwarf companions. The more recently formed of these stars are still surrounded by a planetary nebula. Precise abundance determinations of the various s-process elements, especially, of the lightest, short-lived radionuclide technetium will establish constraints for the formation of s-process elements in asymptotic giant branch stars as well as mass transfer through, for example, stellar wind, Roche-lobe overflow, and common-envelope evolution. We performed a detailed spectral analysis of the K-type subgiant central star of the planetary nebula Hen 2-39 based on high-resolution optical spectra obtained with the Ultraviolet and Visual Echelle Spectrograph at the Very Large Telescope using LTE model atmospheres. We confirm the effective temperature of $T_\\mathrm{eff} = 4350 \\pm 150$ K for the central star of the planetary nebula Hen 2-39. It has a photospheric carbon enrichment of $[\\mathrm{C/H}]= 0.36 \\pm 0.08$ and a barium overabundance of $[\\mathrm{Ba/Fe}]= 1.8 \\pm 0.5$. We find a deficiency for most of the iron-group elements (calcium to iron) and establish an upper abundance limit for technetium ($\\log \\epsilon_\\mathrm{Tc} < 2.5$). The quality of the available optical spectra is not sufficient to measure abundances of all s-process elements accurately. Despite large uncertainties on the abundances as well as on the model yields, the derived abundances are most consistent with a progenitor mass in the range 1.75-3.00 $M_\\odot$ and a metallicity of $[\\mathrm{Fe/H}]= -0.3 \\pm 1.0$. This result leads to the conclusion that the formation of such systems requires a relatively large mass transfer that is most easily obtained via wind-Roche lobe overflow.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2019-02-13T13:31:02.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "planetary nebula hen",
      "barium central star",
      "spectral analysis",
      "s-process elements",
      "k-type subgiant central star"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 26,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}