{
  "id": "1903.03800",
  "version": "v1",
  "published": "2019-03-09T13:25:17.000Z",
  "updated": "2019-03-09T13:25:17.000Z",
  "title": "The chemical compositions and evolutionary status of red giants in the open cluster NGC 6940",
  "authors": [
    "G. Böcek Topcu",
    "M. Afşar",
    "C. Sneden"
  ],
  "comment": "20 pages, 15 figures",
  "journal": "2016MNRAS.463..580B",
  "doi": "10.1093/mnras/stw1974",
  "categories": [
    "astro-ph.SR"
  ],
  "abstract": "We present the high resolution (R $\\approx$ 60000), high signal-to-noise (S/N $\\simeq$ 120) spectroscopic analysis of 12 red giant members of the Galactic open cluster NGC 6940. We applied Yonsei-Yale isochrones to the color-magnitude diagram, which suggested an age of 1.1 Gyr for the cluster with a turn-off mass of 2 M$_{\\odot}$. Atmospheric parameters ($T_{\\rm eff}$, $log~{\\it g}$, [Fe/H] and $\\xi_{t}$) were determined via equivalent widths of Fe I, Fe II, Ti I, and Ti II lines. Calculated mean metallicity of the cluster is $\\langle {\\rm [Fe/H]} \\rangle = 0.04\\pm0.02$. We derived abundances of $\\alpha$ (Mg, Si, Ca), Fe-group (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn), and $n$-capture (Y, La, Nd, Eu) elements to be about solar. Light odd-Z elements Na and Al are slightly enhanced in MMU 108 and MMU 152 by $\\sim$0.34 dex and $\\sim$0.16 dex, respectively. Abundances of light elements Li, C, N, O, and $^{12}$C/$^{13}$C ratios were derived from spectrum syntheses of the Li I resonance doublet at 6707 $\\overset{\\lower.5em\\circ}{\\mathrm{A}}$, [O I] line at 6300 $\\overset{\\lower.5em\\circ}{\\mathrm{A}}$, C$_{2}$ Swan bandheads at 5164 $\\overset{\\lower.5em\\circ}{\\mathrm{A}}$ and 5635 $\\overset{\\lower.5em\\circ}{\\mathrm{A}}$, and strong $^{12,13}$CN system lines in the 7995$-$8040 $\\overset{\\lower.5em\\circ}{\\mathrm{A}}$ region. Most carbon isotopic ratios are similar to those found in other solar-metallicity giants, but MMU 152 has an unusual value of $^{12}$C/$^{13}$C=6. Evaluation of the LiCNO abundances and $^{12}$C/$^{13}$C ratios along with the present theoretical models suggests that all the red giants in our sample are core-helium-burning clump stars.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2019-03-09T13:25:17.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "red giant",
      "evolutionary status",
      "chemical compositions",
      "galactic open cluster ngc",
      "light odd-z elements na"
    ],
    "tags": [
      "journal article"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 20,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}