Journal Article

Abundance and stratification analysis of the chemically peculiar star HD 103498

Chhavi P. Pandey, Denis V. Shulyak, Tanya Ryabchikova and Oleg Kochukhov

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 417, issue 1, pages 444-452
Published in print October 2011 | ISSN: 0035-8711
Published online October 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.19281.x
Abundance and stratification analysis of the chemically peculiar star HD 103498

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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: Teff= 9300 K, log g= 3.5 and Teff= 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 Teff= 9300 K, log g= 3.5, and R= (4.39 ± 0.75) R for Teff= 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 Teff of the star at the current stage of analysis.

Keywords: stars: atmospheres; stars: chemically peculiar; stars: fundamental parameters; stars: individual: HD 103498

Journal Article.  5715 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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