Elemental abundances of the supergiant stars {\sigma} Cygnus and {\eta} Leonis

TL;DR

This paper analyzes the elemental abundances of two supergiant stars, yg and  Leo, using high-resolution spectra and LTE models to determine their atmospheric parameters and chemical compositions.

Contribution

It provides detailed elemental abundance measurements and atmospheric parameters for yg and  Leo, using high-resolution spectra and LTE assumptions, which enhances understanding of supergiant star compositions.

Findings

yg has T_eff=10388 K, log g=1.80, vsini=27 km/s.

 Leo has T_eff=9600 K, log g=2.00, vsini=2 km/s.

Both stars show C deficiency, N overabundance, and O excess.

Abstract

This study aims to analyse the elemental abundances for the late B type supergiant star $\sigma$ Cyg and the early A-type supergiant $\eta$ Leo using ATLAS9 (Kurucz, 1995; Sbordone et al., 2004), assuming local thermodynamic equilibrium (LTE). The spectra used in this study are obtained from Dominion Astrophysical Observatory and have high resolution and signal-to-noise ratios. The effective temperature and the surface gravity of $\sigma$ Cyg are determined from the ionisation equilibria of Al I/II, Mg I/II, Fe I/II, Fe II/III , and by fitting to the wings of H$_\gamma$ and H$_\beta$ profiles as $\textit{T}$$_{eff}$ = 10388 K and log $\textit{g}$ = 1.80. The elemental abundances of $\eta$ Leo} are determined using $\textit{T}$$_{eff}$ = 9600 K and log $\textit{g}$ = 2.00, as reported by Przybilla et al. (2006). The ionisation equilibria of C I/II, N I/II, Mg I/II, Ca I/II, Cr I/II and Fe I/II/III are also satisfied in the atmosphere of $\eta$ Leo. The radial velocities of $\sigma$ Cyg and $\eta$ Leo are -7.25$\pm$7.57 km s$^{-1}$ and 10.40 $\pm$ 13.37 km s$^{-1}$, respectively. The derived projected rotational velocities \textit{vsini} from synthetic spectra are 27 and 2 km s$^{-1}$ for both stars, respectively. The macroturbulent velocities ($\zeta$) are 24 $\pm$ 2 km s$^{-1}$ and 14.5 $\pm$ 1.5 km s$^{-1}$. Also, the microturbulent velocities ($\xi$) have been determined for both of stars as 3.5 km s$^{-1}$. The CNO abundance results of $\sigma$ Cyg and $\eta$ Leo show C deficiency, N overabundance and O in excess.