Na, Al, and O Abundances of Open Clusters NGC 7142, NGC 6939, and IC 4756

Abstract

We present an analysis of echelle spectra of stars in three open clusters obtained with the Hydra multiobject spectrograph on the WIYN 3.5 m telescope. Abundances of Fe, O, Si, Ca, Na, Al, and Ni have been determined via equivalent width analysis and spectrum synthesis. Mean abundances for each cluster are compared to those of previous studies and of other clusters in the literature, with emphasis on exploring the enhancements of Na and Al seen in many open clusters. All three clusters show enhanced values of Na/Fe and Al/Fe, while the abundances of Fe, O, Si, and Ca are consistent with their ages and locations in the Galactic disk.