CARBON-ISOTOPE RATIOS IN VERY LITHIUM-RICH K-GIANTS

High-resolution spectra were used to derive CNO abundances and the C-1 2/C-13 ratios for the very Li-rich K giants HD 19745 and HD 39853. O a nd C-12/C-13 are also obtained for comparison for the Li-rich K giant HD 787. Results from the literature for other very Li-rich giants were also gathered to allow for a more complete discussion. The three most Li-rich giants known, HD 19745, HD 39853, and HD 95799, with epsilon( Li) greater than or equal to 3.0, show low C-12/C-13 values (C-12/C-13 less than or equal to 15), requiring an extra-mixing mechanism, where as HD 9746 and HD 112127 with epsilon(Li) similar to 2.7 show C-12/C-1 3 similar to 25, following the standard first dredge-up predictions. T he data for these five stars indicate that no dear correlation is foun d between C-12/C-13 and epsilon(Li) for the very Li-rich giants. An im portant conclusion is that, since for the three most Li-rich giants, C -12/C-13 is low, efficient mixing should have lowered both C-12/C-13 a nd Li abundances. The very high Li abundances actually found in these stars call therefore for an independent mechanism enriching the Li.