An Extremely Lithium-rich Bright Red Giant in the Globular Cluster M3

We have serendipitously discovered an extremely lithium-rich star on the redgiant branch of the globular cluster M3 (NGC 5272). An echelle spectrumobtained with the Keck I HIRES reveals a Li I 6707 Angstrom resonance doubletof 520 milli-Angstrom equivalent width, and our analysis places the star amongthe most Li-rich giants known: log[epsilon(Li)] ~= +3.0. We determine theelemental abundances of this star, IV-101, and three other cluster members ofsimilar luminosity and color, and conclude that IV-101 has abundance ratiostypical of giants in M3 and M13 that have undergone significant mixing. Wediscuss mechanisms by which a low-mass star may be so enriched in Li, focusingon the mixing of material processed by the hydrogen-burning shell just belowthe convective envelope. While such enrichment could conceivably only happenrarely, it may in fact regularly occur during giant-branch evolution but berarely detected because of rapid subsequent Li depletion.Comment: 7-page LaTeX file, including 2 encapsulated ps figures + 1 table; accepted for publication in the Astrophysical Journal Letter