  aims: Our aim is to determine Li abundances in TO stars of the Globular
Cluster 47 Tuc and test theories about Li variations among TO stars. method: We
make use of high resolution (R~ 43000), high signal-to-noise ratio (S/N=50--70)
spectra of 4 turn off (TO) stars obtained with the UVES spectrograph at the
8.2m VLT Kueyen telescope. results: The four stars observed, span the range
1.6<~A(Li)} <~ 2.14, providing a mean A(Li) = 1.84 with a standard deviation of
0.25 dex. When coupled with data of other two TO stars of the cluster,
available in the literature, the full range in Li abundances observed in this
cluster is 1.6<~A(Li)<~ 2.3. The variation in A(Li) is at least 0.6 dex (0.7
dex considering also the data available in the literature) and the scatter is
six times larger than what expected from the observational error. We claim that
these variations are real. A(Li) seems to be anti-correlated with A(Na) exactly
as observed in NGC 6752. No systematic error in our analysis could produce such
an anti-correlation. conclusions: Na production through p captures on 22Ne at
temperatures in excess of 3x10^7 K and the contemporary Li destruction could
result in this anti-correlation. However such nuclear processing cannot have
taken place in the stars themselves, which do not reach such high temperatures,
even at their centre. This points towards the processing in a previous
generation of stars. The low N/O ratios in the observed stars and the apparent
lack of correlation between N an Li abundances, place a strong constraint on
the properties of this previous generation. Our results indicate a different
behaviour among the Globular Clusters so far studied as far as the abundance
patterns are concerned.
