Yuan-Sen Ting, Gayandhi M. De Silva, Kenneth C. Freeman, Stacey-Jo Parker
We present detailed elemental abundances of 12 subgiants in the open cluster IC 4756 including Na, Al, Mg, Si, Ca, Ti, Cr, Ni, Fe, Zn, Ba. We measure the cluster to have [Fe/H] = -0.01+-0.08. Most of the measured star-to-star [X/H] abundance variation is below sigma < 0.03, as expected from a coeval stellar population preserving natal abundance patterns, supporting the use of elemental abundances as a probe to reconstruct dispersed clusters. We find discrepancies between Cr I and Cr II abundances as well as Ti I and Ti II abundances, where the ionized abundances are larger by about 0.2 dex. This follows other such studies which demonstrate the effects of overionization in cool stars. IC 4756 are super-solar in Mg, Si, Na, Al, but are solar in the other elements. The fact that IC 4756 is super-solar in some alpha-elements (Mg, Si) but solar in the others (Ca, Ti) suggests that the production of alpha-elements is not simply one dimensional and could be exploited for chemical tagging.
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http://arxiv.org/abs/1207.7076
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