Magnetic field, chemical composition and line profile variability of the peculiar eclipsing binary star AR Aur
Abstract
AR Aur is the only eclipsing binary known to contain a HgMn star, making it an ideal case for a detailed study of the HgMn phenomenon. HgMn stars are a poorly understood class of chemically peculiar stars, which have traditionally been thought not to possess significant magnetic fields. However, the recent discovery of line profile variability in some HgMn stars, apparently attributable to surface abundance patches, has brought this belief into question. In this paper we investigate the chemical abundances, line profile variability, and magnetic field of the primary and secondary of the AR Aur system, using a series of high-resolution spectropolarimetric observations. We find the primary is indeed a HgMn star, and present the most precise abundances yet determined for this star. We find the secondary is a weak Am star, and is possibly still on the pre-main sequence. Line profile variability was observed in a range of lines in the primary, and is attributed to inhomogeneous surface distributions of some elements. No magnetic field was detected in any observation of either stars, with an upper limit on the longitudinal magnetic field in both stars of 100 G. Modelling of the phase-resolve longitudinal field measurements leads to a 3σ upper limit on any dipole surface magnetic field of about 400 G.
Based on observations obtained at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France and the University of Hawaii. Also based on observations obtained at the Bernard Lyot Telescope (TBL, Pic du Midi, France) of the Midi-Pyrénées Observatory, which is operated by the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France. E-mail: cpf@arm.ac.uk- Publication:
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Monthly Notices of the Royal Astronomical Society
- Pub Date:
- October 2010
- DOI:
- 10.1111/j.1365-2966.2010.17057.x
- arXiv:
- arXiv:1005.3793
- Bibcode:
- 2010MNRAS.407.2383F
- Keywords:
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- stars: abundances;
- binaries: eclipsing;
- stars: chemically peculiar;
- stars: individual: AR Aur;
- stars: magnetic field;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- Accepted for publication in MNRAS, 11 pages, 9 figures