Hyades giants and

We have discussed only dwarfs so far, but there are four late-G or early-K giants in Hyades (y Tau, 51 Tau, e Tau, and 81 Tau); and Figure 32.5 suggests that the NLTE effect is much less significant for giants than it is for dwarfs. We tried to determine the atmospheric parameters of these stars spectroscopically by using Fe i and Fe ii lines as was done for dwarfs, and found that the metallicities of these giants ([Fe/H] = +0.19, +0.15, +0.10, and +0.13, respectively) spread between +0.1 and +0.2. While these results compare more or less well to the published [Fe/H] values for dwarfs (Figure 32.8(a)), the accuracies of abundance/parameter determinations in this case appear to be comparatively low (e.g. the solutions are sensitive to the choice of lines).

Incidentally, in connection with the topic of giants, we also carried out a similar analysis for Leo (K2 III, a prototype SMR star concerning whose metallicity has been controversial regarding whether it is really SMR; see Figure 32.8(b), which is based on Table 3 of Taylor (2001)) and obtained [Fe/H] = +0.34. Therefore, we may safely conclude that the metallicity of Leo manifestly exceeds that of Hyades, and thus that it deserves the appellation SMR.

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