{
  "id": "2203.05462",
  "version": "v1",
  "published": "2022-03-10T16:35:23.000Z",
  "updated": "2022-03-10T16:35:23.000Z",
  "title": "The Mg-K anti-correlation in Omega Centauri",
  "authors": [
    "Deimer Antonio Alvarez Garay",
    "Alessio Mucciarelli",
    "Carmela Lardo",
    "Michele Bellazzini",
    "Thibault Merle"
  ],
  "comment": "Accepted for publication in ApJL",
  "categories": [
    "astro-ph.SR",
    "astro-ph.GA"
  ],
  "abstract": "We present [K/Fe] abundance ratios for a sample of 450 stars in Omega Centauri, using high resolution spectra acquired with the multi-object spectrograph FLAMES@VLT. Abundances for Fe, Na and Mg were also derived. We detected intrinsic K variations in the analysed stars. Moreover, [K/Fe] shows a significant correlation with [Na/Fe] and anti-correlation with [Mg/Fe]. The presence of a clear-cut Mg-K anti-correlation makes Omega Centauri the third stellar system, after NGC 2419 and NGC 2808, hosting a sub-population of stars with [Mg/Fe]<0.0 dex, K-enriched in the case of Omega Centauri by ~0.3 dex with respect to the Mg-rich stars ([Mg/Fe]>0.0 dex). The correlation/anti-correlation between K and other light elements involved in chemical anomalies supports the idea that the spread in [K/Fe] can be associated to the same self-enrichment process typical of globular clusters. We suggest that significant variations in K abundances perhaps can be found in the most massive and/or metal-poor globular clusters as manifestation of an extreme self-enrichment process. Theoretical models face problems to explain the K production in globular clusters. Indeed, models where asymptotic giant branch stars are responsible for the Mg-K anti-correlation only qualitatively agree with the observations. Finally, we discovered a peculiar star with an extraordinary K overabundance ([K/Fe]=+1.60 dex) with respect to the other stars with similar [Mg/Fe]. We suggest that this K-rich star could be formed from the pure ejecta of AGB stars before dilution with pristine material.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2022-03-10T16:35:23.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "omega centauri",
      "asymptotic giant branch stars",
      "third stellar system",
      "theoretical models face problems",
      "clear-cut mg-k anti-correlation"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}