High-resolution elemental abundance analysis of the open cluster IC 4756

TL;DR

This study provides detailed elemental abundances for stars in the open cluster IC 4756, revealing low star-to-star variation and insights into nucleosynthesis and chemical tagging potential.

Contribution

It offers the first detailed abundance analysis of 12 subgiants in IC 4756, highlighting ionization discrepancies and alpha-element patterns relevant for chemical tagging.

Findings

Star-to-star abundance variation is below 0.03 dex.

Discrepancies between Cr I and Cr II, Ti I and Ti II due to overionization.

IC 4756 is supersolar in Mg, Si, Na, Al, but solar in other elements.

Abstract

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 and Ba. We measure the cluster to have [Fe/H] = -0.01 +/- 0.10. 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 between 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 supersolar in Mg, Si, Na and Al, but are solar in the other elements. The fact that IC 4756 is supersolar 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.