... galaxy

Based on observations collected with the VLT/UT2 Kueyen telescope (Paranal Observatory, ESO, Chile) using the UVES instrument (program ID 71.D-0107).

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...$\rm [M/H]=-0.74$

Here we use the standard notation for the chemical abundance ratio of any element X, [X/H] = log (X/H)$_\star$ - log (X/H)$_\odot$where log (H) $\equiv$ 12 is the abundance of hydrogen by number. In this scale the abundance of any element X is noted as $\epsilon$(X).

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... metallicity

The mean metallicity of the stars [M/H] (Table 3) was obtained as the mean value derived from several lines of Fe, Ti, V, Ni, Cr and Mn.

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... parameters

As commented in the previous section, the derived C/O ratios vary depending on the spectral region analyzed, which probably indicates that something is wrong in the model atmospheres and/or molecular line lists. Note also the possibility of a systematic error due to the uncertain continuum location.

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... stars

The opposite effect would result if the initial C, N and O abundances in the theoretical models are scaled according to the revised solar values by Asplund et al. (2005).

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... C-stars

On the other hand, it would be interesting to derive the C/O ratios in a large sample of CH stars; the only metal-poor (extrinsic) carbon stars where the C/O ratios found are considerably larger than unity (Vanture 1992).

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... factor

The dilution factor is defined as the ratio of the mass transferred from the primary star to the envelope mass of the accreting secondary star, supposed to have the original or post first dredge-up composition.

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...C

For a more detailed discussion of the models see Gallino et al. (1998).

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... lifetime

The value is $\tau_{1/2}\sim 2\times 10^5$ yr.

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... decay

Half-life $\tau_{1/2}\sim 1.5\times 10^6$yr.

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