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The core of the galactic globular cluster 47 Tucanae was observed by the
Faint Object Camera on the refurbished Hubble Space Telescope for the
first time through narrow band F253M and F346M filters centered at
253~nm and 346~nm. A total of 511 stars down to the detection limit at
$m_{346}
\simeq 24$ in the $7^{\prime\prime}
\times 7^{\prime\prime} $
field were accurately placed on a $m_{346}$ vs $m_{253}-m_{346}$ color
magnitude diagram to characterize the stellar populations in the core.
Approximately 100 objects above and to the right of the main sequence
turn-off are the same as those classified earlier with the aberrated HST
but the rest below it are new objects seen now for the first time thanks
to the substantial improvement in sensitivity. The new objects form a
well defined main sequence whose luminosity function turns over
dramatically at $m_{346}
\simeq 20$ well before the completeness limit
and well before the end of the slowly increasing luminosity function for
the outer fields measured from the ground by Hesser et al. (1987). We
interpret this premature drop in the number of stars below $\sim 0.7$
M$_\odot$ in the core as the effect of mass segregation due to two body
relaxation. The position of 9 objects in the range $20< m_{346}<24$ and
$-1.5
