Issue |
A&A
Volume 439, Number 3, September I 2005
|
|
---|---|---|
Page(s) | 1093 - 1098 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20053123 | |
Published online | 12 August 2005 |
Inhomogeneous distribution of mercury on the surfaces of rapidly rotating HgMn stars
1
Department of Astronomy and Space Physics, Uppsala University, 751 20 Uppsala, Sweden e-mail: oleg@astro.uu.se
2
Institute of Astronomy, Russian Academy of Sciences, Pyatnitskaya 48, 119017 Moscow, Russia
3
Special Astrophysical Observatory, Russian Academy of Sciences, Nizhnij Arkhyz, 357147 Karachai-Cherkessian Republic, Russia
Received:
24
March
2005
Accepted:
26
April
2005
Starspots are usually associated with the action of magnetic fields at stellar surfaces.
However, an inhomogeneous chemical distribution of mercury was found recently for the mercury-manganese
(HgMn) star α And – a well-established member of a non-magnetic subclass of the chemically peculiar
stars of the upper main sequence. In this study we present first results of the high-resolution survey of
the 3984 Å resonance line in the spectra of rapidly rotating HgMn stars with atmospheric parameters
similar to those of α And. We use spectrum synthesis modelling and take advantage of the Doppler
resolution of stellar surfaces to probe the horizontal structure of mercury distribution. Clear
signatures of spots are found in the
3984 Å line profiles of HR 1185 and HR 8723. Two observations of
the latter star separated by two days give evidence for line profile variability. We conclude that
inhomogeneous distribution of Hg is a common phenomenon for the rapidly rotating HgMn stars in the
13 000–13 800 K
effective temperature range independent of the stellar evolutionary stage. These results establish
the existence of a new class of spectrum variable spotted B-type stars. It is suggested that the
observed Hg inhomogeneities arise from dynamical instabilities in the chemical diffusion processes and
are unrelated to magnetic phenomena.
Key words: line: profiles / stars: atmospheres / stars: chemically peculiar / stars: individual: HR 1185 / stars: individual: HR 8723
© ESO, 2005
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