All Figures

$\begin{figure} \par\includegraphics[angle=270,width=8.6cm,clip]{3423fig1.eps}\end{figure}$ Figure 1: Temperature structures of the model atmospheres computed with the stellar parameters corresponding to the three stars studied in this work. The points where the optical depth $\log{\tau_{\rm Ross}}=-4,-3,\dots,0$ are indicated by markers. The models corresponding to IGI95-C1 are marked with diamonds, IGI95-C3 with circles and BMB-B 30 with squares. The structure is very sensitive to the carbon excess. The structures computed with the lower value of C/O in Table 3 are plotted with solid lines and markers while the structures with high C/O are indicated with markers only.
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=18cm,clip]{3423fig2.eps}\end{figure}$ Figure 2: Synthetic fits to the spectrum of the star IGI95-C1 in the region around 4825 Å. From this region we derived most of the s-elements abundances and the mean metallicity of the stars. Some atomic lines, main contributors to the specific spectral feature, are marked. Black dots represent the observed spectrum. Lines are synthetic spectra: only molecules and metals (dashed line), and including s-elements (best fit, continuous line).
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In the text

$\begin{figure} \par\includegraphics[origin=rb,angle=-90,width=12cm,clip]{3423fig3.eps}\end{figure}$ Figure 3: Synthetic fit to the spectrum of IGI95-C1 in the region of the Ba II line at $\lambda 4934$ Å. Black dots are the observed spectrum. Lines are synthetic spectra for different [Ba/M] ratios: no Ba and +0.0 (dashed lines), +1.5 (best fit, continuous line).
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In the text

$\begin{figure} \par\includegraphics[origin=rb,angle=-90, width=12cm,clip]{3423fig4.eps}\end{figure}$ Figure 4: Synthetic fit to the spectrum of the star IGI95-C1 in the region around 8025 Å from which we derive the ¹²C/¹³C ratio and a first estimate of the C/O ratio (see text). The ¹³C abundance is estimated from the weaker ¹³CN features at $\lambda \sim 7991$ , 7997, 8004, 8016, 8019, 8023 and 8034 Å. The figure shows only some of these features for clarity. As previous figures, black dots represent the observed spectrum while lines are synthetic spectra for different C/O and ¹²C/¹³C ratios. Dashed lines are for no ¹³C and ¹²C/¹³C = 100 with $\rm C/O =1.18$ , respectively; the continuous line is made with the same C/O ratio and with our best estimate for the ¹²C/¹³C ratio in this star equal to 25. The dotted line represents ¹²C/¹³C = 25 but with $\rm C/O =1.80$ . Clearly, a C/O ratio much larger than unity is discarded.
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In the text

$\begin{figure} \par\includegraphics[angle=-90, width=8.5cm,clip]{3423fig5.ps}\end{figure}$ Figure 5: Comparison of the observed [Rb/Sr] ratio vs. [M/H] with the theoretical predictions for different choices of the ¹³C-pocket (see text) for a 1.5 $M_\odot$ TP-AGB. Continuous line represents the ST (standard) choice while dashed lines limit the area allowed by the choices from ST $\times$ 2 to ST/12. Theoretical models are from Gallino et al. (1998). The stars studied here are marked. The abundance ratios corresponding to IGI95-C3 are not shown because we do not detected Rb in this star. Similar ratios derived in galactic N-type carbon stars (Abia et al. 2001) (black dots at near solar metallicity) are also shown for comparison.
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{3423fig6.eps}\end{figure}$ Figure 6: Comparison of the observed mean of heavy (Ba, La, Nd and Sm) to light-mass (Sr, Y and Zr) s-element [hs/ls] enhancement (signature of the neutron exposure) against metallicity with theoretical prediction for a 1.5 $M_\odot$ TP-AGB. Continuous and dashed lines represent the same as Fig. 5. The location of the stars studied here are marked. At near solar metallicity, the galactic carbon stars studied in Abia et al. (2002, after minor revisions) are shown for comparison.
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In the text

$\begin{figure} \par\includegraphics[origin=rb,angle=-90,width=12cm,clip]{3423fig3.eps}\end{figure}$	Figure 3: Synthetic fit to the spectrum of IGI95-C1 in the region of the Ba II line at $\lambda 4934$ Å. Black dots are the observed spectrum. Lines are synthetic spectra for different [Ba/M] ratios: no Ba and +0.0 (dashed lines), +1.5 (best fit, continuous line).
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