{
  "id": "2501.01909",
  "version": "v1",
  "published": "2025-01-03T17:27:29.000Z",
  "updated": "2025-01-03T17:27:29.000Z",
  "title": "Observations of the Ultraviolet-bright Star III-60 in the Globular Cluster NGC 6723",
  "authors": [
    "William V. Dixon"
  ],
  "comment": "Accepted for publication in ApJ. arXiv admin note: text overlap with arXiv:2312.10248",
  "categories": [
    "astro-ph.SR",
    "astro-ph.GA"
  ],
  "abstract": "We have analyzed archival far-ultraviolet spectra of the UV-bright star III-60 in the globular cluster NGC 6723 obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) and the Cosmic Origins Spectrograph (COS). We find that the star's photospheric parameters (effective temperature $T_{\\rm eff} = 44{,}800 \\pm 1200$, surface gravity $\\log g = 4.89 \\pm 0.18$, and helium abundance $\\log N({\\rm He})/N({\\rm H}) = -0.84 \\pm 0.29$) are consistent with the values derived from its optical spectrum, suggesting that optically-derived values are generally accurate for evolved stars with $T_{\\rm eff} \\lesssim$ 50,000 K. Relative to the cluster's RGB stars, III-60 is enhanced in nitrogen and depleted in carbon and oxygen. The star exhibits strong P Cygni profiles in both components of the N V $\\lambda 1240$ doublet, but the resonance lines of other species show no evidence of a stellar wind. The star's effective temperature and luminosity place it on the evolutionary tracks of stars evolving from the blue horizontal branch, but its high mass ($\\sim 1.2 \\, M_{\\odot}$) indicates that it is the product of a stellar merger. Its helium, carbon, and nitrogen abundances suggest that it is following an evolutionary path similar to that of the low-carbon, intermediate helium-rich hot subdwarfs.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2025-01-03T17:27:29.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "globular cluster ngc",
      "ultraviolet-bright star",
      "observations",
      "far ultraviolet spectroscopic explorer",
      "intermediate helium-rich hot subdwarfs"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}