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Broadband Measurements of the Transverse Magnetic Field of Cool Ap Stars*

Published online by Cambridge University Press:  12 April 2016

J.-L. Leroy ,
J.D. Landstreet ,
E. Landi degl’Innocenti  and
M. Landolfi
J.-L. Leroy
Affiliation:
Observatoire Midi-Pyrénées, 14 ave. Edouard-Belin, 31400 Toulouse, France
J.D. Landstreet
Affiliation:
Department of Astronomy, University of Western Ontario, LondonOntarioCanadaN6A 3K7, and Observatoire Midi-Pyrénées, 14 ave. Edouard Belin, 31400 Toulouse, France
E. Landi degl’Innocenti
Affiliation:
Dipartimento di Astronomia e Scienza dello Spazio, Universita di Firenza, Largo Enrico Fermi 5, 50125 Firenze, Italy
M. Landolfi
Affiliation:
Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Firenze, Italy

Abstract

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Observations of variable broadband linear polarization in magnetic Ap stars (due to the transverse Zeeman effect), when combined with measurements of the mean longitudinal field Bɩ can in some cases allow one to determine the angles i and β (which describe the inclination of the stellar axis of rotation and the obliquity of the magnetic axis to the rotation axis) much more accurately than these angles can be determined from observations of Bɩ alone. Such variable intrinsic linear polarization has been observed for a number of stars; the effect is generally detectable only in cool Ap stars of unusually large field strength. We discuss the data and simple modelling for the stars HD 24712 = HR 1217, HD 137909 = β CrB, and HD 62140 = 49 Cam.

Type
II. Magnetic Fields: Observations and Theories
Information
International Astronomical Union Colloquium , Volume 138: Peculiar versus Normal Phenomena in A-Type and Related Stars , 1993 , pp. 274 - 278
Copyright
Copyright © Astronomical Society of the Pacific 1993

Footnotes

*

Based on observations obtained with the Bernard Lyot Telescope at the Observatoire du Pic-du-Midi, operated by the Observatoire Midi-Pyrénées, Toulouse, France and the Centre National de la Recherche Scientifique.

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