Abundance and stratification analysis of the chemically peculiar star HD 103498

• Published in: Monthly notices of the Royal Astronomical Society Vol. 417; no. 1; pp. 444 - 452
• Main Authors: Pandey, Chhavi P., Shulyak, Denis V., Ryabchikova, Tanya, Kochukhov, Oleg
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.10.2011; Oxford University Press
• Subjects: Astronomy; Atmospheric chemistry; Chemical elements; Stars & galaxies; stars: atmospheres; stars: chemically peculiar; stars: fundamental parameters; stars: individual: HD 103498; stars: atmospheres; stars: fundamental parameters; stars: individual: HD 103498; stars: chemically peculiar
• ISSN: 0035-8711; 1365-2966; 1365-2966
• DOI: 10.1111/j.1365-2966.2011.19281.x

The slow rotation and the absence of strong mixing processes in the atmospheres of chemically peculiar stars develop the ideal conditions for the appearance of abundance anomalies through the mechanism of microscopic particle diffusion. This makes these objects look spectroscopically and photometrically different from their 'normal' analogues. As a result, it is often difficult to accurately determine the atmospheric parameters of these stars, and special methods are needed for a consistent analysis of their atmospheres. The main aim of the present paper is to analyse atmospheric abundance and stratification of chemical elements in the atmosphere of the chemically peculiar star HD 103498. We find that there are two model atmospheres, computed with individual and stratified abundances, that provide a reasonable fit to the observed spectroscopic and photometric indicators: T eff= 9300 K, log g= 3.5 and T eff= 9500 K, log g= 3.6. It is shown that Mg has a large abundance gradient in the star's atmosphere with accumulation of Mg ions in the uppermost atmospheric layers, whereas Si demonstrates the opposite behaviour with accumulation in deep layers. In addition, a detailed non-local thermodynamic equilibrium (non-LTE) analysis showed that none of the Mg transitions under consideration is a subject of noticeable non-LTE effects. By comparing the photometry observations after transforming them to physical units, we estimated the radius of HD 103498 to be between R= (4.56 ± 0.77) R⊙ for T eff= 9300 K, log g= 3.5, and R= (4.39 ± 0.75) R⊙ for T eff= 9500 K, log g= 3.6 models, respectively. We note that the lack of suitable observations in absolute units prevents us from uniquely determining the T eff of the star at the current stage of analysis.