Journal Article

Abundances and search for vertical stratification in the atmospheres of four HgMn stars

M. Thiam, F. LeBlanc, V. Khalack and G. A. Wade

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 405, issue 2, pages 1384-1396
Published in print June 2010 | ISSN: 0035-8711
Published online June 2010 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2010.16539.x
Abundances and search for vertical stratification in the atmospheres of four HgMn stars

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Using high-resolution, high-signal-to-noise ratio archival UVES (Ultraviolet-Visual Echelle Spectrograph) spectra, we have performed a detailed spectroscopic analysis of four chemically peculiar HgMn stars (HD 71066, HD 175640, HD 178065 and HD 221507). Using spectrum synthesis, mean photospheric chemical abundances are derived for 22 ions of 16 elements. We find good agreement between our derived abundances and those published previously by other authors. For the five elements that present a sufficient number of suitable lines, we have attempted to detect vertical chemical stratification by analyzing the dependence of derived abundance as a function of optical depth. For most elements and most stars, we find no evidence of chemical stratification with typical 3σ upper limits of Δ log Nelem/Ntot∼ 0.1–0.2 dex per unit optical depth. However, for Mn in the atmosphere of HD 178065 we find convincing evidence of stratification. Modelling of the line profiles using a two-step model for the abundance of Mn yields a local abundance varying approximately linearly by ∼0.7 dex through the optical depth range log τ5000=−3.6 to −2.8.

Keywords: stars: abundances; stars: chemically peculiar; stars: individual: HD 71066 (κ2 Vel); stars: individual: HD 175640 (HR 7143); stars: individual: HD 178065 (HR 7245); stars: individual: HD 221507 (β Scl)

Journal Article.  8042 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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