Volume 568, August 2014
|Number of page(s)||6|
|Published online||08 August 2014|
Measuring the surface magnetic fields of magnetic stars with unresolved Zeeman splitting⋆
1 Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany
2 School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, UK
Received: 8 April 2014
Accepted: 7 July 2014
Aims. High-dispersion, archival spectra of magnetic Ap stars with resolved Zeeman components in Stokes I are used to derive a simple relation that can be utilised to estimate the mean surface field strengths of stars with v sin i ≳ 10 km s-1.
Methods. For each star, the mean surface field, as measured from the observed splitting in Fe ii at 6149 Å, is compared to the differential broadening of spectral lines with large and small Landé factors in order to produce a relation to estimate the field strengths of magnetic stars with unresolved Zeeman patterns.
Results. The method is shown to be reliable for rotational velocities up to about 50 km s-1 for field strengths down to about 5 kG.
Conclusions. These results should allow for better constraints to be placed on the mean surface magnetic fields of Ap stars where Zeeman patterns are unresolved.
Key words: stars: magnetic field / stars: chemically peculiar
Based on observations made with the European Southern Observatory telescopes under ESO programmes 60.A-9036(A), 68.D-0254(A), 69.D-0378(A), 074.D-0392(A), 075.C-0234(A), 075.C-0234(B), 076.C-0073(A), 076.D-0169(A), 077.D-0477(A), 079.D-0118(A), 079.C-0170(A), 079.C-0170(B), 080.C-0032(A), 080.C-0032(B), 081.C-0034(A), 081.C-0034(B), 082.C-0218(A), 082.C-0308(A), 089.C-0207(A), 089.D-0383(A), 266.D-5655(A), obtained from the ESO/ST-ECF Science Archive Facility. 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 Science de l’Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii. Based in part on observations available on the ELODIE archive.
© ESO, 2014
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