Barium abundances of A--F--G type stars in the Hyades cluster

TL;DR

This study measures barium abundances in Hyades cluster stars, revealing nearly constant values in G stars and significant overabundance with dispersion in A stars, influenced by temperature and rotation, with a depression around 6500K.

Contribution

It provides detailed spectroscopic analysis of Ba abundances in Hyades stars, highlighting the parameter dependence and anomaly characteristics across spectral types.

Findings

G stars have nearly constant Ba abundance (~+0.2 dex above solar).

A stars show large Ba overabundance and dispersion correlated with Teff and vsini.

F stars exhibit a Ba abundance depression around 6500K, near the Li-dip region.

Abstract

With an aim of clarifying the extent and parameter-dependence of compositional anomaly of barium in A-type stars, Ba abundances were spectroscopically determined based on BaII 6141/6496 lines for 89 (23 A-type and 66 F--G-type) main-sequence stars belonging to the members of Hyades cluster by taking into account the non-LTE effect and the hyper-fine-structure effect. While the non-LTE effect tends to strengthen lines in G stars, it acts in the direction of line weakening in the regime of A stars due to increasing imortance of overionization. The Ba abundances of G stars turned out almost constant (<A>= 2.33), indicating that the primordial composition of Ba in Hyades is mildly supersolar by ~+0.2dex. In contrast, A-type stars show Ba overabundances of considerably large dispersion (0~<[Ba/H]~<2). Since this Ba excess tends to increase with an increase/decrease in Teff/vsini, these two parameters may be essential for producing or controling the anomaly. Regarding Hyades F-type stars, their Ba abundances are not uniform but show a broad depression (by <~0.3dex) around Teff~6500K, interestingly coinciding with the location of Li-dip.