| Issue |
A&A
Volume 523, November-December 2010
|
|
|---|---|---|
| Article Number | A40 | |
| Number of page(s) | 5 | |
| Section | Stellar atmospheres | |
| DOI | https://doi.org/10.1051/0004-6361/201014848 | |
| Published online | 16 November 2010 | |
No detection of large-scale magnetic fields at the surfaces of Am and HgMn stars⋆
1
Laboratoire d’Astrophysique de Toulouse-Tarbes, CNRS, Université de
Toulouse,
57 avenue d’Azereix,
65008
Tarbes,
France
e-mail: michel.aurier@ast.obs-mip.fr;
ligniere;@ast.obs-mip.fr; alain.hui@ast.obs-mip.fr; donati@ast.obs-mip.fr; petit@ast.obs-mip.fr; roudier@ast.obs-mip.fr; stheado@ast.obs-mip.fr
2
Department of Physics, Royal Military College of Canada, PO Box 17000, Station Forces,
Kingston, Ontario
K7K 4B4,
Canada
e-mail: gregg.wade@rmc.ca
3
Department of Physics & Astronomy, The University of
Western Ontario, London, Ontario,
N6A 3K7,
Canada
e-mail: jlandstr@uwo.ca
4
Armagh Observatory, College Hill, Armagh BT61 9DG, Northern Ireland,
UK
e-mail: jls@arm.ac.uk
5
Institute of Astronomy, Bulgarian Academy of Sciences,
72 Tsarigradsko
shose, 1784
Sofia,
Bulgaria
e-mail: iliani@astro.bas.bg
Received:
22
April
2010
Accepted:
12
August
2010
Aims. We investigate the magnetic dichotomy between Ap/Bp and other A-type stars by carrying out a deep spectropolarimetric study of Am and HgMn stars.
Methods. Using the NARVAL spectropolarimeter at the Télescope Bernard Lyot (Observatoire du Pic du Midi, France), we obtained high-resolution circular polarisation spectroscopy of 12 Am stars and 3 HgMn stars.
Results. Using least squares deconvolution (LSD), no magnetic field is detected in any of the 15 observed stars. Uncertaintiies as low as 0.3 G (respectively 1 G) have been reached for surface-averaged longitudinal magnetic field measurements for Am (respectively HgMn) stars.
Conclusions. Associated with the results obtained previously for Ap/Bp stars, our study confirms the existence of a magnetic dichotomy among A-type stars. Our data demonstrate that there is at least one order of magnitude difference in field strength between Zeeman detected stars (Ap/Bp stars) and non Zeeman detected stars (Am and HgMn stars). This result confirms that the spectroscopically-defined Ap/Bp stars are the only A-type stars harbouring detectable large-scale surface magnetic fields.
Key words: stars: chemically peculiar / stars: magnetic field / stars: peculiar / stars: early-type
© ESO, 2010
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