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 T _ { eff } range of \sim 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 like the case of Fe : \langle [ C/H ] \rangle = +0.15 ( \sigma = 0.08 ) , \langle [ O/H ] \rangle = +0.22 ( \sigma = 0.14 ) , and \langle [ Fe/H ] \rangle = +0.11 ( \sigma = 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 T _ { eff } ( typically on the order of \sim 10 ^ { -4 } dex K ^ { -1 } ) ; while this might be due to an improper choice of atmospheric parameters , we found it hard to give a quantitatively reasonable explanation .
Regarding Li , we confirmed the well-known T _ { eff } -dependent trend in the Li abundance reported so far ( a conspicuous Li-trough at 6300 K \ltsim T _ { eff } \ltsim 6700 K and a progressive decrease toward a lower T _ { eff } at T _ { eff } \ltsim 6000 K ) , which means that the surface Li of Hyades stars is essentially controlled only by T _ { eff } and other parameters such as the rotational velocity are almost irrelevant .