2023MNRAS.518.4038H

The origin of the so-called weak G-band stars constitutes an unsolved problem in stellar astrophysics. In this context, we present a detailed abundance analysis of a new weak G-band star, HD 16424, which stands out with a very low ¹²C/¹³C ratio and Li and Na overabundance. Our work is based on the high-resolution échelle spectrum (R ≈ 48 000) and includes photometric and astrometric data from the literature. The analysis adopted in this work is performed under local thermodynamic equilibrium (LTE) approximation; we determine the atmospheric parameters (T_eff, $\log \, g$, [Fe/H], and ξ), abundances for proton-capture elements (C, N, O, Li), s-process elements (Y, Zr, La), and mixing tracers such as the ¹²C/¹³C isotopic ratio and sodium abundance, following by NLTE corrections applied to Li, O, and Na abundances. Our results show ¹²C deficiency ([C/Fe] = -0.57) and N enrichment ([N/Fe] = +0.97), that is typical for weak G-band stars. Also, we notice a carbon isotopic ratio characteristic of the CN-cycle equilibrium (〈¹²C/¹³C〉 = 4.0) and high lithium-7 abundance ($\log \, \varepsilon$(Li)_NLTE = 2.85). In addition, this study shows a low projected rotational velocity ($v\, \sin \, i$ = 2.0 km s^–1) and low mass (1.61 M_⊙) of HD 16424, which distinguishes this star from the intermediate-mass objects found in this class of peculiar objects.