{
  "id": "1003.3419",
  "version": "v1",
  "published": "2010-03-17T17:55:49.000Z",
  "updated": "2010-03-17T17:55:49.000Z",
  "title": "The central star of the planetary nebula PB 8: a Wolf-Rayet-type wind of an unusual WN/WC chemical composition",
  "authors": [
    "H. Todt",
    "M. Peña",
    "W. -R. Hamann",
    "G. Gräfener"
  ],
  "comment": "10 pages, 10 figures",
  "categories": [
    "astro-ph.SR"
  ],
  "abstract": "A considerable fraction of the central stars of planetary nebulae (CSPNe) are hydrogen-deficient. As a rule, these CSPNe exhibit a chemical composition of helium, carbon, and oxygen with the majority showing Wolf-Rayet-like emission line spectra. These stars are classified as CSPNe of a spectral type [WC]. We perform a spectral analysis of CSPN PB 8 with the Potsdam Wolf-Rayet (PoWR) models for expanding atmospheres. The source PB 8 displays wind-broadened emission lines from strong mass loss. Most strikingly, we find that its surface composition is hydrogen-deficient, but not carbon-rich. With mass fractions of 55% helium, 40% hydrogen, 1.3% carbon, 2% nitrogen, and 1.3% oxygen, it differs greatly from the 30-50% of carbon which are typically seen in [WC]-type central stars. The atmospheric mixture in PB 8 has an analogy in the WN/WC transition type among the massive Wolf-Rayet stars. Therefore we suggest to introduce a new spectral type [WN/WC] for CSPNe, with PB 8 as its first member. The central star of PB 8 has a relatively low temperature of T=52kK, as expected for central stars in their early evolutionary stages. Its surrounding nebula is less than 3000 years old, i.e. relatively young. Existing calculations for the post-AGB evolution can produce hydrogen-deficient stars of the [WC] type, but do not predict the composition found in PB 8. We discuss various scenarios that might explain the origin of this unique object.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2010-03-17T17:55:49.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "central star",
      "unusual wn/wc chemical composition",
      "planetary nebula pb",
      "wolf-rayet-type wind",
      "wolf-rayet-like emission line spectra"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1051/0004-6361/200912183",
      "journal": "Astronomy and Astrophysics",
      "year": 2010,
      "month": "Jun",
      "volume": 515
    },
    "note": {
      "typesetting": "TeX",
      "pages": 10,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 849146,
      "adsabs": "2010A&A...515A..83T"
    }
  }
}