All Figures

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{3298f1a.eps}\hspace*{4mm} \includegraphics[width=7.8cm,clip]{3298f1b.eps}\end{figure}$ Figure 1: Left panel a): evolutionary tracks of Schaller et al. (1992) compared with the locations of classical barium stars (stars labelled "G'' in Mennessier et al. (1997); open dots) and the yellow SyS AG Dra (filled circle), BD $-21^\circ 3873$ (filled triangle) and Hen 2-467 (filled square). The bolometric magnitudes were taken from the references listed in Table 1. These bolometric magnitudes were combined with bolometric corrections from Bessell et al. (1998) and B-V indices from Munari et al. (1992) and Munari & Buson (1992) to yield the absolute visual magnitudes. Right panel b): same as a) but for YSyS (filled symbols as in the left panel) and metal-deficient barium stars [open triangles: stars flagged as "H'' by Mennessier et al. (1997); crosses: CH stars also flagged as "H'' by Mennessier et al. (1997); small open squares: additional metal-deficient, s-process-rich stars from Table 2; open circle: HD 104340, large open square: HD 206983 from Junqueira & Pereira (2001)]. The dashed horizontal line represents the luminosity ( $M_{\rm bol} = -3$ , corresponding to $M_{\rm V} \sim -2$ ) at the first thermal pulse in a 1 $M_\odot$ AGB star of metallicity [Fe/H] = -1.8according to Lattanzio (1991).
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In the text

$\begin{figure} \par\includegraphics[width=7.6cm,clip]{3298f2.eps}\end{figure}$ Figure 2: $H_{\alpha }$ profiles for two candidate metal-deficient Ba stars (HD 139409 and HD 148897; see however the discussion in Sect. 3), compared to that of the K giant Arcturus. The wavelength scale has been corrected for the stellar radial velocity. The profiles show no indication of symbiotic activity.
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In the text

$\begin{figure} \par\includegraphics[width=7.4cm,clip]{3298f3.eps}\end{figure}$ Figure 3: Comparison of equivalent widths measured on the HARPS spectrum of Arcturus with those of the Arcturus spectral atlas (Hinkle et al. 2000), for the same set of lines as that measured in HD 139409.
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In the text

$\begin{figure} \par\includegraphics[width=7.6cm,clip]{3298f4.eps}\end{figure}$ Figure 4: The spectra of the target stars in the region of the Ba II line at 614.172 nm. Measured lines are marked. Also shown is the spectrum of the standard star Arcturus (Hinkle et al. 2000).
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In the text

$\begin{figure} \par\includegraphics[width=7.9cm,clip]{3298f5.eps}\end{figure}$ Figure 5: The iron abundances derived from Fe I (open circles) and Fe II (filled circles) lines are displayed as a function of the excitation potential for the lower energy level of the line. The absence of a trend in these data is used to derive the spectroscopic temperature of HD 139409.
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In the text

$\begin{figure} \par\includegraphics[width=7.9cm,clip]{3298f6.eps}\end{figure}$ Figure 6: The abundances derived from the Fe I (open circles) and Fe II (filled circles) lines are displayed as a function of the line equivalent widths. The absence of a trend in these data is used to derive the microturbulent velocity of HD 139409.
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{3298f7.eps}\end{figure}$ Figure 7: Abundance pattern in HD 139409 (abundances derived from ionized species are represented by black dots, and from neutral species by crosses).
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In the text

$\begin{figure} \par\includegraphics[width=7.45cm,clip]{3298f8.eps}\end{figure}$ Figure 8: Radial velocities as a function of heliocentric Julian Day for BD +4 $^\circ$ 2466, superimposed on the orbital solution corresponding to the orbital elements listed in Table 6.
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In the text

$\begin{figure} \par\includegraphics[width=7.5cm,clip]{3298f9.eps}\end{figure}$ Figure 9: Radial velocities as a function of heliocentric Julian Day for HIP 58596 = HD 104340 (open circles correspond to measurements obtained with the southern CORAVEL, and filled circles with the northern one).
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In the text

$\begin{figure} \par\includegraphics[width=7.45cm,clip]{3298f10.eps}\end{figure}$ Figure 10: Radial velocities as a function of heliocentric Julian Day for BD +3 $^\circ$ 2688.
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In the text

$\begin{figure} \par\includegraphics[width=7.5cm,clip]{3298f11.eps}\end{figure}$ Figure 11: Radial velocities as a function of heliocentric Julian Day for HIP 34795 = HD 55496. The symbols are as in Fig. 9. With respect to the data listed in Table 7, an offset of -1 km s^-1 has been applied to the northern measurements to make them consistent with the southern ones.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{3298f12a.eps}\hspace*{3mm} \... ...12c.eps}\hspace*{3mm} \includegraphics[width=8cm,clip]{3298f12d.eps}\end{figure}$ Figure 12: The $\alpha$ statistics (Eq. (6)) as a function of the trial orbital period (assuming e = 0) for metal-deficient barium stars. The period from the spectroscopic orbit (represented by an arrow) of HIP 29740 (upper left panel) indeed lies within the range of minimum $\alpha$ values. By comparison, the suspected binaries HIP 97874 and HIP 107478 are likely to have periods $P \sim 800$ d and $\sim$ 250-450 d, respectively. For comparison, stars non-flagged as binaries have no (e, P, T) grid points with $\alpha < 0.02$ (see Fig. 13). The vertical dashed lines represent multiple, or integer fractions, of 1 y. At those periods, there is a strong correlation between the parallactic and orbital signals, which degrades the $\alpha$ statistics and makes binaries difficult to find at those 1-y alias periods.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{3298f13a.eps}\hspace*{3mm} \includegraphics[width=8cm,clip]{3298f13b.eps}\end{figure}$ Figure 13: Same as Fig. 12 for HIP 34795 ( left panel, flagged as binary) and HIP 58596 ( right panel, non-binary).
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In the text

$\begin{figure} \par\includegraphics[width=7.3cm,clip]{3298f14.eps}\end{figure}$ Figure 14: Comparison of the period distributions for samples of binary systems with different kinds of red giant primaries: S stars (Jorissen et al. 1998), red SyS (excluding symbiotic novae and symbiotic Miras; Mürset & Schmid 1999), M giants (Jorissen et al. 2004a) and K giants (Mermilliod 1996). The lower two panels present the orbital-period distribution for barium stars (Jorissen et al. 1998) and yellow SyS (Mürset & Schmid 1999). In the S star panel, the arrow marked H $_\alpha$ indicates the period range where binary S stars exhibit H $_\alpha$ emission as a signature of weak symbiotic activity. The shaded area marks stars with only a lower limit available on their orbital period. The numbers in the upper right corner of each panel correspond to the sample size.
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In the text

$\begin{figure} \par\includegraphics[width=7.6cm,clip]{3298f2.eps}\end{figure}$	Figure 2: $H_{\alpha }$ profiles for two candidate metal-deficient Ba stars (HD 139409 and HD 148897; see however the discussion in Sect. 3), compared to that of the K giant Arcturus. The wavelength scale has been corrected for the stellar radial velocity. The profiles show no indication of symbiotic activity.
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$\begin{figure} \par\includegraphics[width=7.4cm,clip]{3298f3.eps}\end{figure}$	Figure 3: Comparison of equivalent widths measured on the HARPS spectrum of Arcturus with those of the Arcturus spectral atlas (Hinkle et al. 2000), for the same set of lines as that measured in HD 139409.
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$\begin{figure} \par\includegraphics[width=7.6cm,clip]{3298f4.eps}\end{figure}$	Figure 4: The spectra of the target stars in the region of the Ba II line at 614.172 nm. Measured lines are marked. Also shown is the spectrum of the standard star Arcturus (Hinkle et al. 2000).
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$\begin{figure} \par\includegraphics[width=7.9cm,clip]{3298f5.eps}\end{figure}$	Figure 5: The iron abundances derived from Fe I (open circles) and Fe II (filled circles) lines are displayed as a function of the excitation potential for the lower energy level of the line. The absence of a trend in these data is used to derive the spectroscopic temperature of HD 139409.
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$\begin{figure} \par\includegraphics[width=7.9cm,clip]{3298f6.eps}\end{figure}$	Figure 6: The abundances derived from the Fe I (open circles) and Fe II (filled circles) lines are displayed as a function of the line equivalent widths. The absence of a trend in these data is used to derive the microturbulent velocity of HD 139409.
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$\begin{figure} \par\includegraphics[width=7.8cm,clip]{3298f7.eps}\end{figure}$	Figure 7: Abundance pattern in HD 139409 (abundances derived from ionized species are represented by black dots, and from neutral species by crosses).
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$\begin{figure} \par\includegraphics[width=7.45cm,clip]{3298f8.eps}\end{figure}$	Figure 8: Radial velocities as a function of heliocentric Julian Day for BD +4 $^\circ$ 2466, superimposed on the orbital solution corresponding to the orbital elements listed in Table 6.
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$\begin{figure} \par\includegraphics[width=7.5cm,clip]{3298f9.eps}\end{figure}$	Figure 9: Radial velocities as a function of heliocentric Julian Day for HIP 58596 = HD 104340 (open circles correspond to measurements obtained with the southern CORAVEL, and filled circles with the northern one).
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$\begin{figure} \par\includegraphics[width=7.45cm,clip]{3298f10.eps}\end{figure}$	Figure 10: Radial velocities as a function of heliocentric Julian Day for BD +3 $^\circ$ 2688.
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$\begin{figure} \par\includegraphics[width=7.5cm,clip]{3298f11.eps}\end{figure}$	Figure 11: Radial velocities as a function of heliocentric Julian Day for HIP 34795 = HD 55496. The symbols are as in Fig. 9. With respect to the data listed in Table 7, an offset of -1 km s^-1 has been applied to the northern measurements to make them consistent with the southern ones.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{3298f13a.eps}\hspace*{3mm} \includegraphics[width=8cm,clip]{3298f13b.eps}\end{figure}$	Figure 13: Same as Fig. 12 for HIP 34795 ( left panel, flagged as binary) and HIP 58596 ( right panel, non-binary).
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