Elemental abundances of intermediate-age open cluster NGC 3680

Authors

  • A. W. Mitschang,

    Corresponding author
    1. Macquarie University Research Centre in Astronomy, Astrophysics & Astrophotonics NSW 2109, Australia
    2. Department of Physics & Astronomy, Macquarie University, NSW 2109, Australia
      E-mail: arik.mitschang@mq.edu.au
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  • G. M. De Silva,

    1. Australian Astronomical Observatory, PO Box 296, Epping, NSW 1710, Australia
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  • D. B. Zucker

    1. Macquarie University Research Centre in Astronomy, Astrophysics & Astrophotonics NSW 2109, Australia
    2. Department of Physics & Astronomy, Macquarie University, NSW 2109, Australia
    3. Australian Astronomical Observatory, PO Box 296, Epping, NSW 1710, Australia
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Based on observations obtained at the European Southern Observatory, Paranal, Chile [ESO programme 072.B-0331(B)].

E-mail: arik.mitschang@mq.edu.au

ABSTRACT

We present a new abundance analysis of the intermediate-age Galactic open cluster NGC 3680, based on high-resolution, high signal-to-noise ratio VLT/UVES spectroscopic data. Several element abundances are presented for this cluster for the first time, but most notably we derive abundances for the light and heavy s-process elements Y, Ba, La and Nd. The serendipitous measurement of the rare-earth r-process element Gd is also reported. This cluster exhibits a significant enhancement of Na in giants as compared to dwarfs, which may be a proxy for an O to Na anticorrelation as observed in Galactic globular clusters but not open clusters. We also observe a step-like enhancement of heavy s-process elements towards higher atomic number, contrary to expectations from asymptotic giant branch nucleosynthesis models, suggesting that the r process played a significant role in the generation of both La and Nd in this cluster.

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