Journal Article

Vertical stratification of iron in atmospheres of blue horizontal-branch stars

V. Khalack, F. LeBlanc and B. B. Behr

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 407, issue 3, pages 1767-1772
Published in print September 2010 | ISSN: 0035-8711
Published online September 2010 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2010.17008.x
Vertical stratification of iron in atmospheres of blue horizontal-branch stars

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The aim of this study is to search for observational evidence of vertical iron stratification in the atmosphere of 14 blue horizontal-branch (BHB) stars. We have found from our numerical simulations that five BHB stars: B22, B186 in the globular cluster NGC 288, WF 2−820, WF 2−2692 in M13 and B203 in M15 show clear signatures of the vertical stratification of iron whose abundance increases toward the lower atmosphere. Two other BHB stars (B334 in M15 and B176 in M92) also show possible iron stratification in their atmosphere. A dependence of the slope of iron stratification on the effective temperature was also discovered. It is found that the vertical stratification of iron is strongest in BHB stars with Teff around 11 500 K. The slope of iron abundance decreases as Teff increases and becomes negligible for the BHB stars with Teff≈ 14 000 K. These results support the hypothesis regarding the efficiency of atomic diffusion in the stellar atmospheres of BHB stars with Teff≽ 11 500 K.

Keywords: stars: atmospheres; stars: chemically peculiar; stars: horizontal branch

Journal Article.  4203 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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