All Figures

$\begin{figure} \par\includegraphics[width=12cm,clip]{1254fig1.eps} \end{figure}$ Figure 1: UVES spectra of the two turn-off stars A228 and A2111 of the globular cluster NGC 6397. The dotted lines correspond to the best-fit Be abundances $\log$ (Be/H) = -12.27 for A228 and $\log$ (Be/H) = -12.43for A2111. The dashed lines correspond to synthetic spectra with abundances of $\pm$ 0.2 dex from the best fitting abundance. For comparison, we also show the spectrum of the bright halo star HD 218502, whose atmospheric parameters are close to those of the NGC 6397 TO stars. The best fit synthetic spectrum for this star corresponds to $\log$ (Be/H) = -12.36.
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In the text

$\begin{figure} \par\includegraphics[width=7.2cm,clip]{1254fig2.ps} \end{figure}$ Figure 2: UVES spectra of stars A2111 and A228 in the oxygen triplet region. The two stars have identical atmospheric parameters, but the O abundance differs almost by 0.6 dex.
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{1254fig3.ps} \end{figure}$ Figure 3: UVES spectra of stars A2111 and A228 around the NH band at 336 nm. For comparison, we also show the same spectral region for our reference star HD 218502, whose atmospheric parameters ( $T_{\rm eff}=6296$ K, $\log~ g=4.13$ , [Fe/H] = -1.85) are close to those of the NGC 6397 TO stars. While the band (whose core region is indicated by the dashed lines) is virtually absent in the reference star, it is well pronounced in the two cluster stars, indicating a strong N overabundance.
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In the text

$\begin{figure} \par\includegraphics[width=9.1cm,height=8.8cm,clip,angle=270]{1254fig4.ps} \end{figure}$ Figure 4: Be abundance vs. oxygen for the NGC 6397 TO stars (filled circles) and the star from B99, (open circles).
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{1254fig5.ps} \end{figure}$ Figure 5: Evolution of beryllium with time in the Galaxy according to a three-zone Galactic chemical evolution model (Valle et al. 2002). The three curves refer to the halo, thick disk, and thin disk. The data points show the beryllium abundance in the young open cluster IC 2391 (age 30 Myr), the Sun (age 4.5 Gyr), and the globular cluster NGC 6397. The model result is normalized to the solar meteoritic abundance. The inset illustrate the use of beryllium as a "cosmic clock'' to constrain the formation of NGC 6397. The horizontal lines corresponds to the 1 $\sigma$ counturs around the measured beryllium abundance. The cluster birth is constrained to the first 0.2-0.3 Gyr after the onset of star formation in the Galactic halo.
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In the text

$\begin{figure} \par\includegraphics[width=7.2cm,clip]{1254fig2.ps} \end{figure}$	Figure 2: UVES spectra of stars A2111 and A228 in the oxygen triplet region. The two stars have identical atmospheric parameters, but the O abundance differs almost by 0.6 dex.
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$\begin{figure} \par\includegraphics[width=9.1cm,height=8.8cm,clip,angle=270]{1254fig4.ps} \end{figure}$	Figure 4: Be abundance vs. oxygen for the NGC 6397 TO stars (filled circles) and the star from B99, (open circles).
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