The Abundance of Lithium in an ABG Star in the Globular Cluster M3 (NGC 5272)

Abstract

A survey of red giants in the globular cluster M3 with the Hydra multi-object spectrograph on the WIYN 3.5 m telescope indicated a prominent Li i 6707 Å feature in the red giant vZ 1050. Followup spectroscopy with the ARC 3.5 m telescope confirmed this observation and yielded a derived abundance of A(Li)NLTE = 1.6 ± 0.05. In addition, the high oxygen and low sodium abundances measured from the same spectrum suggest that vZ 1050 is a first generation cluster star. The location of vZ 1050 above the horizontal branch and blueward of the red giant branch in the cluster’s color–magnitude diagram places vZ 1050 on M3's asymptotic giant branch. The likely source for the enhanced lithium abundance is the Cameron–Fowler mechanism operating in vZ 1050 itself.