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The search for magnetic fields in mercury-manganese stars

Published online by Cambridge University Press:  12 July 2011

Vitalii Makaganiuk ,
Oleg Kochukhov ,
Nikolai Piskunov ,
Sandra V. Jeffers ,
Christopher M. Johns-Krull ,
Christoph U. Keller ,
Michiel Rodenhuis ,
Frans Snik ,
Henricus C. Stempels  and
Jeff A. Valenti
Vitalii Makaganiuk
Affiliation:
Department Physics and Astronomy, Uppsala University, Uppsala, Sweden
Oleg Kochukhov
Affiliation:
Department Physics and Astronomy, Uppsala University, Uppsala, Sweden
Nikolai Piskunov
Affiliation:
Department Physics and Astronomy, Uppsala University, Uppsala, Sweden
Sandra V. Jeffers
Affiliation:
Sterrekundig Instituut, Universiteit Utrecht, Utrecht, The Netherlands
Christopher M. Johns-Krull
Affiliation:
Department of Physics and Astronomy, Rice University, Houston, TX, USA
Christoph U. Keller
Affiliation:
Sterrekundig Instituut, Universiteit Utrecht, Utrecht, The Netherlands
Michiel Rodenhuis
Affiliation:
Sterrekundig Instituut, Universiteit Utrecht, Utrecht, The Netherlands
Frans Snik
Affiliation:
Sterrekundig Instituut, Universiteit Utrecht, Utrecht, The Netherlands
Henricus C. Stempels
Affiliation:
Department Physics and Astronomy, Uppsala University, Uppsala, Sweden
Jeff A. Valenti
Affiliation:
Space Telescope Science Institute, San Martin Dr, Baltimore, MD, USA
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Abstract

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Mercury-manganese (HgMn) stars were considered to be non-magnetic, showing no evidence of surface spots. However, recent investigations revealed that some stars in this class possess an inhomogeneous distribution of chemical elements on their surfaces. According to our current understanding, the most probable mechanism of spot formation involves magnetic fields. Taking the advantage of a newly-built polarimeter attached to the HARPS spectrometer at the ESO 3.6m-telescope, we performed a high-precision spectropolarimetric survey of a large group of HgMn stars. The main purpose of this study was to find out how typical it is for HgMn stars to have weak magnetic fields. We report no magnetic field detection for any of the studied objects, with a typical precision of the longitudinal field measurements of 10 G and down to 1 Gauss for some of the stars. We conclude that HgMn stars lack large-scale magnetic fields typical of spotted magnetic Ap stars and probably lack any fields capable of creating and sustaining chemical spots. Our study confirms that alongside the magnetically altered atomic diffusion, there must be other structure formation mechanism operating in the atmospheres of late-B main sequence stars.

Keywords

instrumentation: polarimetersstars: magnetic fieldsstars: chemically peculiar
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 6 , Symposium S272: Active OB stars: structure, evolution, mass loss, and critical limits , July 2010 , pp. 202 - 203
Copyright
Copyright © International Astronomical Union 2011

References

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