{
  "id": "1012.4802",
  "version": "v1",
  "published": "2010-12-21T21:00:00.000Z",
  "updated": "2010-12-21T21:00:00.000Z",
  "title": "Direct Evidence for an Enhancement of Helium in Giant Stars in Omega Centauri",
  "authors": [
    "A. K. Dupree",
    "Jay Strader",
    "Graeme H. Smith"
  ],
  "comment": "ApJ in press. 29 pages, 11 figures",
  "categories": [
    "astro-ph.SR",
    "astro-ph.GA"
  ],
  "abstract": "The double main sequence identified in the globular cluster Omega Centauri has been interpreted using isochrones to indicate a large variation in the abundance of helium. If true, a helium enhancement carries strong implications for the chemical and stellar evolutionary history of this cluster. However, only indirect measures currently support this conjecture. We report the discovery of a variation in the line strength of the near-infrared He I 10830 A transition in twelve similar red giants in Omega Centauri observed with PHOENIX on Gemini-S. Abundances of these stars derived from Magellan/MIKE spectra taken at Las Campanas Observatory show that the helium transition is not detected in the most metal-poor population ([Fe/H] < -1.8), yet is present in the majority of stars with [Fe/H] >= -1.8. These observations give the first direct evidence for an enhancement of helium in Omega Centauri. The appearance of helium appears better correlated with increased [Al/Fe] and [Na/Fe] abundances than as a function of [Fe/H], giving observational support to the presence of high-temperature H-burning in a prior generation of stars.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2010-12-21T21:00:00.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "giant stars",
      "helium enhancement carries strong implications",
      "globular cluster omega centauri",
      "first direct evidence",
      "helium appears better"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1088/0004-637X/728/2/155",
      "journal": "The Astrophysical Journal",
      "year": 2011,
      "month": "Feb",
      "volume": 728,
      "number": 2,
      "pages": 155
    },
    "note": {
      "typesetting": "TeX",
      "pages": 29,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 882212,
      "adsabs": "2011ApJ...728..155D"
    }
  }
}