Lithium, carbon, and oxygen abundances of hyades F-G type stars*

Abstract

In an attempt to carry out a systematic study on the behavior of the photospheric abundances of Li, C, and O (along with Fe) for Hyades main-sequence stars in the Teff range of ̃ 5000-7000 K, we conducted an extensive spectrum-synthesis analysis applied to four spectral regions (comprising lines of Fe-group elements, Li I 6708 line, C I 7111-7119 lines, and O I 6156-8 lines), based on the high-dispersion spectra of 68 selected F-G type stars belonging to this cluster. The abundances of C and O turned out to be fairly uniform in a marginally supersolar level, such as like the case of Fe: h[C=H]i = +0.15 (σ = 0.08), h[O=H]i = +0.22 (σ = 0.14), and h[Fe=H]i = +0.11 (σ = 0.08), suggesting that the primordial abundances are almost retained for these elements. Strictly, however, they show a slightly increasing trend with a decrease in Teff (typically on the order of ̃10-4 dexK-1); while this might be due to an improper choice of atmospheric parameters, we found it difficult to give a quantitatively reasonable explanation. Regarding Li, we confirmed the well-known Teff-dependent trend in the Li abundance reported so far (a conspicuous Li-trough at 6300K̃Teff̃6700K and a progressive decrease toward a lower Teff at Teff̃6000 K), which means that the surface Li of Hyades stars is essentially controlled only by Teff ; other parameters, such as the rotational velocity, are almost irrelevant. © 2013. Astronomical Society of Japan.