Lithium Abundances of the Super-Metal-Rich Open Cluster NGC 6253

TL;DR

This study investigates lithium abundances in the super-metal-rich open cluster NGC 6253, revealing how metallicity influences lithium depletion and providing insights into stellar evolution and Galactic lithium production.

Contribution

It presents the first detailed lithium abundance analysis of a super-metal-rich cluster, expanding understanding of metallicity effects on stellar lithium depletion.

Findings

Higher metallicity correlates with greater lithium depletion.

The Li gap's position in temperature is independent of metallicity.

The Li gap's position does not evolve with age.

Abstract

High-resolution CTIO 4-m/HYDRA spectroscopy of the super-metal-rich open cluster NGC 6253 ([Fe/H]=+0.43+/-0.01) has been used to study the stellar lithium (Li) abundances near the cluster's turnoff. NGC 6253 greatly expands the range of [Fe/H] for clusters that have a Li abundance analysis. This is important for studying the complicated effects of, and potential correlations with, stellar Fe abundance on surface Li abundance. Comparisons to the younger and less-metal-rich Hyades and to the similarly-aged but solar-metallicity M67 show that NGC 6253's Li abundances are qualitatively consistent with the prediction, from Standard Stellar Evolution Theory, that higher-metallicity stars have a greater Li depletion. Comparison with M67 provides evidence that the more-metal-rich NGC 6253 had a higher initial Li, which is consistent with expectations from models of Galactic Li production. NGC 6253 is also compared to the intermediate-aged NGC 3680, NGC 752, and IC 4651 open clusters. Comparison of the Li-gap positions in all six clusters shows: a) the gap's position in Teff is independent of metallicity, but b) higher-metallicity clusters have their gaps in higher-mass stars. In addition, the Li gap's position is shown not to evolve with age, which provides an important constraint for the non-standard depletion mechanisms that may create the Li gap.