{
  "id": "1501.00874",
  "version": "v1",
  "published": "2015-01-05T14:15:33.000Z",
  "updated": "2015-01-05T14:15:33.000Z",
  "title": "Mass loss on the red giant branch: the value and metallicity dependence of Reimers' η in globular clusters",
  "authors": [
    "Iain McDonald",
    "Albert Zijlstra"
  ],
  "comment": "Accepted MNRAS",
  "categories": [
    "astro-ph.SR"
  ],
  "abstract": "The impact of metallicity on the mass-loss rate from red giant branch (RGB) stars is studied through its effect on the parameters of horizontal branch (HB) stars. The scaling factors from Reimers (1975) and Schroder & Cuntz (2005) are determined for 56 well-studied Galactic globular clusters (GCs). The median values among clusters are, respectively, {\\eta}_R = 0.477 +/- 0.070 (+0.050/-0.062) and {\\eta}_SC = 0.172 +/- 0.024 (+0.018/-0.023) (standard deviation and systematic uncertainties, respectively). Mass-loss mechanisms on the RGB have very little metallicity dependence: over a factor of 200 in iron abundance, {\\eta} varies by <~30 per cent, within the current systematic uncertainties on cluster ages and evolution models. Since {\\eta} incorporates cluster age, the low standard deviation of {\\eta} among clusters (~14 per cent) suggests that age can almost entirely account for the \"second parameter problem\". The remaining spread in {\\eta} correlates with cluster mass and density, suggesting helium enrichment provides the third parameter explaining HB morphology of GCs. The metallicity variation is reduced further if globular clusters are more co-eval than generally thought. This would also better reproduce the observed AGB tip luminosities, which are not well modelled by extrapolating the RGB {\\eta} to later evolutionary epochs.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2015-01-05T14:15:33.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "red giant branch",
      "globular clusters",
      "metallicity dependence",
      "mass loss",
      "third parameter explaining hb morphology"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}