Akademik Veri Yönetim Sistemi
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, cilt.461, sa.4, ss.4071-4087, 2016 (SCI-Expanded)
We have derived elemental abundances of a remarkable star, HD 179821, with unusual composition (e. g. [Na/Fe] = 1.0 +/- 0.2 dex) and extra-ordinary spectral characteristics. Its metallicity at [Fe/H] = 0.4 dex places it among the most metal-rich stars yet analysed. The abundance analysis of this luminous star is based on high-resolution and high-quality (S/N approximate to 120-420) optical echelle spectra from McDonald Observatory and Special Astronomy Observatory. The data includes five years of observations over 21 epochs. Standard 1D local thermodynamic equilibrium analysis provides a fresh determination of the atmospheric parameters over all epochs: T-eff = 7350 +/- 200 K, log g= +0.6 +/- 0.3, and a microturbulent velocity. = 6.6 +/- 1.6 km s(-1) and [Fe/H] = 0.4 +/- 0.2, and a carbon abundance [C/Fe] = -0.19 +/- 0.30. We find oxygen abundance [O/Fe] = -0.25 +/- 0.28 and an enhancement of 0.9 dex in N. A supersonic macroturbulent velocity of 22.0 +/- 2.0 km s(-1) is determined from both strong and weak Fe I and Fe II lines. Elemental abundances are obtained for 22 elements. HD 179821 is not enriched in s-process products. Eu is overabundant relative to the anticipated [X/Fe] approximate to 0.0. Some peculiarities of its optical spectrum (e.g. variability in the spectral line shapes) is noticed. This includes the line profile variations for Ha line. Based on its estimated luminosity, effective temperature and surface gravity, HD 179821 is a massive star evolving to become a red supergiant and finally a Type II supernova.