All Figures

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{1892f01.eps} \end{figure}$ Figure 1: The observed solar spectrum (Kurucz et al. 1984), shown as a continuous line, with superimposed the synthetic spectrum obtained using the adopted line list and the solar model (dotted line), in the G-band region at $\sim$ 4309-18 Å. Notice that the spectral region shown in this figure is less than 1/4 of that used in our comparison with synthetic spectra.
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{1892f02.eps} \end{figure}$ Figure 2: Left panel: spectrum synthesis of some features of the CH band in a subgiant star of 47 Tuc. The heavy solid line is the observed spectrum, while dashed, solid and dotted lines are the synthetic spectra computed for three values of the C abundances (listed on top of the figure). Right panel: the same, for a dwarf star of 47 Tuc. Note that the synthetic spectra are now computed with different C values. All synthetic spectra were convolved with a Gaussian to take into account the instrumental profile of observed spectra.
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{1892f03.eps} \end{figure}$ Figure 3: The observed solar spectrum (Kurucz et al. 1984), shown as a continuous line, with superimposed the synthetic spectrum obtained using the adopted line list and the solar model (dotted line), in the region at $\sim$ 3880 Å including the $\Delta v=0$ bandheads of UV CN transition.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{1892f04.eps} \end{figure}$ Figure 4: The observed spectrum of the subgiant 206 810 in NGC 6397 (heavy solid line) in the spectral region 3400-3410 Å. The thin solid lines are synthetic spectra computed by using values of [N/Fe] = 1.0, 1.25, 1.50, 1.75 and 2.0 from top to bottom, respectively. The NH lines are clearly observed.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{1892f05.eps} \end{figure}$ Figure 5: The same as in previous figure but for the average spectrum of 3 dwarfs in NGC 6397, namely stars 202765, 201432 and 1543.
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{1892f06.eps} \end{figure}$ Figure 6: [C/Fe] ratio as a function of [N/Fe] for stars in 47 Tuc (red triangles), NGC 6752 (green circles) and NGC 6397 (blue squares). Open symbols represent dwarfs and filled symbols are subgiant stars, for all three clusters. Arrows represent upper limits in N, C abundances. Typical error bars are also shown.
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{1892f07.eps} \end{figure}$ Figure 7: [C/Fe] ratio as a function of [N/Fe]. For our stars in 47 Tuc, NGC 6397 and NGC 6752 symbols are as in Fig. 6, with typical error bars shown. For literature data (all smaller symbols), filled yellow circles are SGB stars in M 5 from Cohen et al. (2002), black crosses are main sequence turn-off stars in M 13 from Briley et al. (2004a), magenta empty triangles are M 71 turn-off stars from Briley & Cohen (2001) and magenta empty exploded stars are 47 Tuc MS stars from Briley et al. (2004b).
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{1892f08.eps} \par\end{figure}$ Figure 8: [C/Fe] ratio as a function of absolute magnitude for program stars in NGC 6397, NGC 6752 and 47 Tuc. Symbols are as in Fig. 6. Small (magenta) crosses are the field stars of the Gratton et al. (2000) sample with metallicity in the range $\rm -2.0 \leq [Fe/H] \leq -1$ .
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{1892f09.eps} \end{figure}$ Figure 9: [C/Fe] ratio as a function of absolute magnitude for program stars in NGC 6397, NGC 6752 and 47 Tuc. Symbols are as in Fig. 6. Small (magenta) crosses are the field stars of the Gratton et al. (2000) sample with metallicity in the range $-2.0 \leq$ [Fe/H] $\leq -1$ . Open (blue) diamonds are the bright giants in NGC 6397 from Briley et al. (1990); open (green) diamonds are red giants in NGC 6752 from Suntzeff & Smith (1991); open (red) diamonds are red giants in 47 Tuc from Brown et al. (1990).
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{1892f10.eps} \end{figure}$ Figure 10: [N/Fe] ratio as a function of absolute magnitude for program stars in NGC 6397, NGC 6752 and 47 Tuc, field stars (Gratton et al. 2000) and cluster red giants from the literature (Brown et al. 1990). Symbols and color codes are as in the previous figure.
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{1892f11.eps} \end{figure}$ Figure 11: Isotopic ratio ¹²C/¹³C as a function of M_V for program stars in NGC 6397, NGC 6752 and 47 Tuc. Symbols are as in the previous figures. Small (magenta) crosses and upper limits are the field stars of the Gratton et al. (2000) sample with metallicity in the range $-2.0 \leq$ [Fe/H] $\leq -1$ . Open (green) diamonds are red giants in NGC 6752 from Suntzeff & Smith (1991); open (red) diamonds are red giants in 47 Tuc from Brown et al. (1990) and Shetrone (2003).
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{1892f12.eps} \end{figure}$ Figure 12: [Na/Fe] ratio as a function of [O/Fe], for stars in 47 Tuc, NGC 6752 and NGC 6397. Symbols for our program stars are as in Fig. 6. Literature data are as follows: (green) diamonds with crosses inside are bright red giants from the extensive study by Yong et al. (2003), open (blue, green and red) diamonds are stars of NGC 6397, NGC 6752 and 47 Tuc, respectively, from Norris & Da Costa (1995), Carretta (1994) and Castilho et al. (2000), as described in the text.
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{1892f13.eps} \end{figure}$ Figure 13: [C/Fe] ratio as a function of [Na/Fe], for stars in 47 Tuc, NGC 6397 and NGC 6752. Symbols are as in Fig. 6.
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{1892f14.eps} \end{figure}$ Figure 14: [N/Fe] ratio as a function of [Na/Fe], for stars in 47 Tuc, NGC 6752 and NGC 6397. Symbols are as in Fig. 6.
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{1892f15.eps} \end{figure}$ Figure 15: [N/Fe] ratio as a function of [O/Fe], for stars in 47 Tuc, NGC 6752 and NGC 6397. Symbols are as in Fig. 6.
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{1892f16.eps} \end{figure}$ Figure 16: [C/Fe] ratio as a function of [(C+N)/Fe]. For our stars in 47 Tuc, NGC 6397 and NGC 6752 symbols are as in Fig. 6. For literature data (all smaller symbols), filled yellow circles are SGB stars in M 5 from Cohen et al. (2002), black crosses are main sequence turn-off stars in M 13 from Briley et al. (2004a), magenta empty triangles are M 71 turn-off stars from Briley & Cohen (2001) and magenta empty exploded stars are 47 Tuc MS stars from Briley et al. (2004b).
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{1892f17.eps} \end{figure}$ Figure 17: [N/Fe] ratio as a function of [(C+N+O)/Fe] for our stars in 47 Tuc, NGC 6397 and NGC 6752; symbols are as in Fig. 6.
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{1892f18.eps} \end{figure}$ Figure 18: [C/N] ratio as a function of [O/N] for our stars in 47 Tuc, NGC 6397 and NGC 6752; symbols are as in Fig. 6. Superimposed on the data are the three models outlined in the text: a simple dilution with material processed through the complete CNO cycle (solid, black line), contamination from N-poor RGB stars (dashed blue line) with composition typical of field RGB stars, and contamination from N-rich upper-RGB stars experiencing very deep mixing (dotted magenta line).
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{1892f01.eps} \end{figure}$	Figure 1: The observed solar spectrum (Kurucz et al. 1984), shown as a continuous line, with superimposed the synthetic spectrum obtained using the adopted line list and the solar model (dotted line), in the G-band region at $\sim$ 4309-18 Å. Notice that the spectral region shown in this figure is less than 1/4 of that used in our comparison with synthetic spectra.
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$\begin{figure} \par\includegraphics[width=8.8cm,clip]{1892f03.eps} \end{figure}$	Figure 3: The observed solar spectrum (Kurucz et al. 1984), shown as a continuous line, with superimposed the synthetic spectrum obtained using the adopted line list and the solar model (dotted line), in the region at $\sim$ 3880 Å including the $\Delta v=0$ bandheads of UV CN transition.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{1892f04.eps} \end{figure}$	Figure 4: The observed spectrum of the subgiant 206 810 in NGC 6397 (heavy solid line) in the spectral region 3400-3410 Å. The thin solid lines are synthetic spectra computed by using values of [N/Fe] = 1.0, 1.25, 1.50, 1.75 and 2.0 from top to bottom, respectively. The NH lines are clearly observed.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{1892f05.eps} \end{figure}$	Figure 5: The same as in previous figure but for the average spectrum of 3 dwarfs in NGC 6397, namely stars 202765, 201432 and 1543.
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$\begin{figure} \par\includegraphics[width=8.8cm,clip]{1892f06.eps} \end{figure}$	Figure 6: [C/Fe] ratio as a function of [N/Fe] for stars in 47 Tuc (red triangles), NGC 6752 (green circles) and NGC 6397 (blue squares). Open symbols represent dwarfs and filled symbols are subgiant stars, for all three clusters. Arrows represent upper limits in N, C abundances. Typical error bars are also shown.
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$\begin{figure} \par\includegraphics[width=8.8cm,clip]{1892f08.eps} \par\end{figure}$	Figure 8: [C/Fe] ratio as a function of absolute magnitude for program stars in NGC 6397, NGC 6752 and 47 Tuc. Symbols are as in Fig. 6. Small (magenta) crosses are the field stars of the Gratton et al. (2000) sample with metallicity in the range $\rm -2.0 \leq [Fe/H] \leq -1$ .
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$\begin{figure} \par\includegraphics[width=8.8cm,clip]{1892f10.eps} \end{figure}$	Figure 10: [N/Fe] ratio as a function of absolute magnitude for program stars in NGC 6397, NGC 6752 and 47 Tuc, field stars (Gratton et al. 2000) and cluster red giants from the literature (Brown et al. 1990). Symbols and color codes are as in the previous figure.
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$\begin{figure} \par\includegraphics[width=8.8cm,clip]{1892f13.eps} \end{figure}$	Figure 13: [C/Fe] ratio as a function of [Na/Fe], for stars in 47 Tuc, NGC 6397 and NGC 6752. Symbols are as in Fig. 6.
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$\begin{figure} \par\includegraphics[width=8.8cm,clip]{1892f14.eps} \end{figure}$	Figure 14: [N/Fe] ratio as a function of [Na/Fe], for stars in 47 Tuc, NGC 6752 and NGC 6397. Symbols are as in Fig. 6.
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$\begin{figure} \par\includegraphics[width=8.8cm,clip]{1892f15.eps} \end{figure}$	Figure 15: [N/Fe] ratio as a function of [O/Fe], for stars in 47 Tuc, NGC 6752 and NGC 6397. Symbols are as in Fig. 6.
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$\begin{figure} \par\includegraphics[width=8.8cm,clip]{1892f17.eps} \end{figure}$	Figure 17: [N/Fe] ratio as a function of [(C+N+O)/Fe] for our stars in 47 Tuc, NGC 6397 and NGC 6752; symbols are as in Fig. 6.
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