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arXiv · 1512.04557

Elemental abundances of the supergiant stars σ Cygnus and η Leonis

Taner Tanriverdi
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Abstract

This study aims to analyse the elemental abundances for the late B type supergiant star $σ$ Cyg and the early A-type supergiant $η$ 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 $σ$ 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$_γ$ and H$_β$ profiles as $\textit{T}$$_{eff}$ = 10388 K and log $\textit{g}$ = 1.80. The elemental abundances of $η$ Leo} are determined using $\textit{T}$$_{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 $η$ Leo. The radial velocities of $σ$ Cyg and $η$ 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 ($ζ$) are 24 $\pm$ 2 km s$^{-1}$ and 14.5 $\pm$ 1.5 km s$^{-1}$. Also, the microturbulent velocities ($ξ$) have been determined for both of stars as 3.5 km s$^{-1}$. The CNO abundance results of $σ$ Cyg and $η$ Leo show C deficiency, N overabundance and O in excess.

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Taner Tanriverdi. 2015-12-14. Elemental abundances of the supergiant stars σ Cygnus and η Leonis. https://doi.org/10.1016/j.newast.2013.03.013

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