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Magnetic fields and chemical peculiarities of the very young intermediate-mass binary system HD 72106
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics.
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2008 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, Vol. 391, no 2, 901-914 p.Article in journal (Refereed) Published
Abstract [en]

The recently discovered magnetic Herbig Ae and Be stars may provide qualitatively new information about the formation and evolution of magnetic Ap and Bp stars. We have performed a detailed investigation of one particularly interesting binary system with a Herbig Ae secondary and a late B-type primary possessing a strong, globally ordered magnetic field. 20 high-resolution Stokes V spectra of the system were obtained with the ESPaDOnS instrument mounted on the Canada-France-Hawaii Telescope. In these observations we see clear evidence for a magnetic field in the primary, but no evidence for a magnetic field in the secondary. A detailed abundance analysis was performed for both stars, revealing strong chemical peculiarities in the primary and normal chemical abundances in the secondary. The primary is strongly overabundant in Si, Cr and other iron-peak elements, as well as Nd, and underabundant in He. The primary therefore appears to be a very young Bp star. In this context, line profile variations of the primary suggest non-uniform lateral distributions of surface abundances. Interpreting the 0.639 95 +/- 0.000 09 d variation period of the Stokes I and V profiles as the rotational period of the star, we have modelled the magnetic field geometry and the surface abundance distributions of Si, Ti, Cr and Fe using magnetic Doppler imaging. We derive a dipolar geometry of the surface magnetic field, with a polar strength B-d = 1230 G and an obliquity beta = 57 degrees. The distributions Ti, Cr and Fe are all qualitatively similar, with an elongated patch of enhanced abundance situated near the positive magnetic pole. The Si distribution is somewhat different, and its relationship to the magnetic field geometry less clear.

Place, publisher, year, edition, pages
2008. Vol. 391, no 2, 901-914 p.
Keyword [en]
stars: abundances, stars: chemically peculiar, stars: evolution, stars: individual: HD 72106, stars: magnetic fields
National Category
Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:uu:diva-107025DOI: 10.1111/j.1365-2966.2008.13946.xISI: 000261265300035OAI: oai:DiVA.org:uu-107025DiVA: diva2:227576
Available from: 2009-07-15 Created: 2009-07-15 Last updated: 2009-07-15Bibliographically approved

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