* Astronomy

Title: Elemental abundances of intermediate age open cluster NGC 3680
Authors: A. W. Mitschang (1), G. M. De Silva (2), D. B. Zucker (1,2) ((1) Macquarie University Research Centre in Astronomy, Astrophysics & Astrophotonics, (2) Australian Astronomical Observatory)

We present a new abundance analysis of the intermediate age Galactic open cluster NGC 3680, based on high resolution, high signal-to-noise 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 anti-correlation 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 AGB 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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