Lithium in a cool red giant member of the globular cluster NGC 362

A surprisingly strong Li I lambda 6707 feature has been identified in a red giant member of the globular cluster NGC 362. This giant, V2, is located n ear the tip of the red giant branch and could be either a first-ascent red giant or on the asymptotic giant branch. An abundance analysis finds the li thium abundance to be log epsilon(Li) = 1.2 +/-. 0.2. Since almost all low- mass giants have destroyed and diluted their photospheric lithium abundance s to much lower levels, the source of lithium in star V2 is a mystery. The solution to this mystery is suggested to reside in two possible mechanisms. The proposed deep-mixing mechanism called "cool bottom processing" can acc ount for the observed lithium at this giant's luminosity [log (L/L.) = 3.3] if the parameterized mixing speed, measured as log(dM/dt), is similar to-5 .5 (in units of M. yr(-1)). An alternative source of the excess lithium cou ld be the ingestion, into the red giant's convective envelope, of an simila r to 0.04 M. object with an assumed undepleted, typical halo lithium abunda nce of log epsilon(Li) = 2.2.