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Frank Grundahl

Iron and neutron-capture element abundance variations in the globular cluster M2 (NGC 7089)

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  • David Yong, Research School of Astronomy and Astrophysics, Australian National University, Canberra
  • ,
  • Ian U. Roederer, Department of Astronomy, University of Michigan
  • ,
  • Frank Grundahl
  • Gary S. Da Costa, Research School of Astronomy and Astrophysics, Australian National University, Canberra, Denmark
  • Amanda I. Karakas, Research School of Astronomy and Astrophysics, Australian National University, Canberra
  • ,
  • John E. Norris, Research School of Astronomy and Astrophysics, Australian National University, Canberra
  • ,
  • Wako Aoki, National Astronomical Observatory, Mitaka, Tokyo, Denmark
  • Cherie K. Fishlock, Research School of Astronomy and Astrophysics, Australian National University, Canberra, Denmark
  • A. F. Marino, Research School of Astronomy and Astrophysics, Australian National University, Canberra
  • ,
  • A. P. Milone, Research School of Astronomy and Astrophysics, Australian National University, Canberra
  • ,
  • Luke J. Shingles, Research School of Astronomy and Astrophysics, Australian National University, Canberra, Denmark
We present CN and CH indices and Ca II triplet metallicities for 34 giant stars and chemical abundances for 33 elements in 14 giants in the globular cluster M2. Assuming that the programme stars are cluster members, our analysis reveals (i) an extreme variation in CN and CH line strengths, (ii) a metallicity dispersion with a dominant peak at [Fe/H] ≈ -1.7 and smaller peaks at -1.5 and -1.0, (iii) star-to-star abundance variations and correlations for the light elements O, Na, Al and Si and (iv) a large (and possibly bimodal) distribution in the abundances of all elements produced mainly via the s-process in Solar system material. Following Roederer, Marino & Sneden, we define two groups of stars, `r + s' and `r-only', and subtract the average abundances of the latter from the former group to obtain an `s-process residual'. This s-process residual is remarkably similar to that found in M22 and in M4 despite the range in metallicity covered by these three systems. With recent studies identifying a double subgiant branch in M2 and a dispersion in Sr and Ba abundances, our spectroscopic analysis confirms that this globular cluster has experienced a complex formation history with similarities to M22, NGC 1851 and ω Centauri.
Original languageEnglish
JournalRoyal Astronomical Society. Monthly Notices
Volume441
Issue4
Pages (from-to)3396-3416
Number of pages21
ISSN0035-8711
DOIs
Publication statusPublished - 1 Jul 2014

    Research areas

  • stars: abundances, Galaxy: abundances, globular clusters: individual: NGC 7089

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