High-resolution spectroscopic analysis of four unevolved barium stars

Abstract

A classical Local Thermodynamic Equilibrium analysis, based on high-resolution spectroscopic data, is performed for a sample of three potential barium dwarf candidates and one star already recognized as such. We derived their atmospheric parameters, estimated their masses and luminosities, and determined chemical abundances for a set of 21 elements, including CNO. Some elemental abundances are derived for the first time in HD~15096, HD~37792, and HD~141804. The program stars are dwarfs/subgiants with metallicities typical of disc stars, exhibiting moderate carbon enhancements, with $[C/Fe]$ ratios ranging from $+0.29$ to $+0.66$ dex, and high levels of \textit{slow} neutron-capture ($s$-process) elements, with $[\text{s}/Fe]\gtrsim +1.0$~dex. As spectroscopic binaries, their peculiarities are attributable to mass transfer events. The observed neutron-capture patterns of were individually compared with two sets of $s$-process nucleosynthesis models (Monash and {\sc fruity}), yielding dilution factors and masses estimates for the former polluting Asymptotic Giant Branch stars. Low-mass ($\lesssim 3.0{\mathrm{M}}_{\odot }$) models successfully reproduce the observations. In addition, we estimated mean neutron exposures of the order of 0.6 -- 0.7 mb${}^{-1}$ for the $s$-processed material observed in their envelopes. Applying an empirical initial-final mass relation, we constraint in $\sim 0.7{\text{M}}_{\odot }$ the mass of their dim white-dwarf companions. Moreover, our kinematic study revealed that the program stars are members of the thin disk, with probabilities greater than 70\%. Hence, we identified HD~15096 and HD~37792 as new barium dwarfs and confirmed that HD~141804 is a barium dwarf. Thus, the number of barium dwarfs identified in the literature from high-resolution spectroscopy increases to 71 objects.

29 pages, 10 figures, accepted for publication in The Astronomical Journal