Lithium, Carbon, and Oxygen Abundances of Hyades F-G Type Stars

TL;DR

This study systematically analyzes the photospheric abundances of lithium, carbon, and oxygen in Hyades F-G stars, revealing mostly uniform primordial levels with slight T_eff-dependent trends, and confirms the known T_eff-dependent lithium pattern.

Contribution

It provides a comprehensive spectral analysis of Li, C, and O in Hyades stars, highlighting their near-primordial uniformity and T_eff-related abundance trends, which were not previously detailed for this cluster.

Findings

C and O abundances are fairly uniform and slightly supersolar.

Li abundance shows a T_eff-dependent trend with a trough between 6300K and 6700K.

Surface Li is mainly controlled by T_eff, with little influence from rotational velocity.

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 T_eff range of ~5000-7000K, 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: <[C/H]> = +0.15 (sigma = 0.08), <[O/H]> = +0.22 (sigma = 0.14), and <[Fe/H]> = +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 ~10^(-4) dex/K; 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 6300K <T_eff< 6700K and a progressive decrease toward a lower T_eff at T_eff < 6000K), 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.