{
  "id": "1210.2566",
  "version": "v1",
  "published": "2012-10-09T11:31:22.000Z",
  "updated": "2012-10-09T11:31:22.000Z",
  "title": "Carbon and nitrogen abundances of stellar populations in the globular cluster M 2",
  "authors": [
    "C. Lardo",
    "E. Pancino",
    "A Mucciarelli",
    "A. P. Milone"
  ],
  "comment": "15 pages, 14 figures; accepted for publication in A&A",
  "categories": [
    "astro-ph.SR",
    "astro-ph.GA"
  ],
  "abstract": "We present CH and CN index analysis and C and N abundance calculations based on the low-resolution blue spectra of red giant branch (RGB) stars in the Galactic globular cluster NGC 7089 (M 2). Our main goal is to investigate the C-N anticorrelation for this intermediate metallicity cluster. The data were collected with DOLORES, the multiobject, low-resolution facility at the Telescopio Nazionale Galileo. Spectroscopic data were coupled with UV photometry obtained during the spectroscopic run. We found a considerable star-to-star variation in both A(C) and A(N) at all luminosities for our sample of 35 targets. These abundances appear to be anticorrelated, with a hint of bimodality in the C content for stars with luminosities below the RBG bump (V~15.7), while the range of variations in N abundances is very large and spans almost ~ 2 dex. We find additional C depletion as the stars evolve off the RGB bump, in fairly good agreement with theoretical predictions for metal-poor stars in the course of normal stellar evolution. We isolated two groups with N-rich and N-poor stars and found that N abundance variations correlate with the (U-V) color in the DOLORES color-magnitude diagram (CMD). The V, (U-V) CMD for this cluster shows an additional RGB sequence, located at the red of the main RGB and amounting to a small fraction of the total giant population. We identified two CH stars detected in previous studies in our U, V images. These stars, which are both cluster members, fall on this redder sequence, suggesting that the anomalous RGB should have a peculiar chemical pattern. Unfortunately, no additional spectra were obtained for stars in this previously unknown RGB branch.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2012-10-09T11:31:22.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "stellar populations",
      "nitrogen abundances",
      "galactic globular cluster ngc",
      "telescopio nazionale galileo",
      "low-resolution blue spectra"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1051/0004-6361/201220129",
      "journal": "Astronomy and Astrophysics",
      "year": 2012,
      "month": "Dec",
      "volume": 548
    },
    "note": {
      "typesetting": "TeX",
      "pages": 15,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 1189954,
      "adsabs": "2012A&A...548A.107L"
    }
  }
}