We have serendipitously discovered an extremely lithium-rich star on the red giant branch of the globular cluster M3 (NGC 5272). An echelle spectrum obtained with the Keck I HIRES reveals a Li I 6707 Angstrom resonance doublet of 520 milli-Angstrom equivalent width, and our analysis places the star among the most Li-rich giants known: log[epsilon(Li)] ~= +3.0. We determine the elemental abundances of this star, IV-101, and three other cluster members of similar luminosity and color, and conclude that IV-101 has abundance ratios typical of giants in M3 and M13 that have undergone significant mixing. We discuss mechanisms by which a low-mass star may be so enriched in Li, focusing on the mixing of material processed by the hydrogen-burning shell just below the convective envelope. While such enrichment could conceivably only happen rarely, it may in fact regularly occur during giant-branch evolution but be rarely detected because of rapid subsequent Li depletion.
@article{arxiv.astro-ph/9904152,
title = {An Extremely Lithium-Rich Bright Red Giant in the Globular Cluster M3},
author = {Robert P. Kraft and Ruth C. Peterson and Puragra Guhathakurta and Christopher Sneden and Jon P. Fulbright and G. Edward Langer},
journal= {arXiv preprint arXiv:astro-ph/9904152},
year = {2009}
}
Comments
7-page LaTeX file, including 2 encapsulated ps figures + 1 table; accepted for publication in the Astrophysical Journal Letters