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Observations of Magnetically Split Lines in Ap Stars*)

Published online by Cambridge University Press:  12 April 2016

Gautier Mathys ,
John D. Landstreet  and
Thierry Lanz
Gautier Mathys
Affiliation:
European Southern Observatory, Casilla 19001, Santiago 19, Chile
John D. Landstreet
Affiliation:
Department of Astronomy, University of Western Ontario, LondonOntarioCanadaN6A 3K7, and Observatoire Midi-Pyrénées, 14 avenue Edouard Belin, F-31400 Toulouse, France
Thierry Lanz
Affiliation:
NASA Goddard Space Flight Center, Code 681, Greenbelt, MD 20771, USAandInstitut d’Astronomie de l’Université de Lausanne, CH-1290 Chavannes-des-Bois, Switzerland

Abstract

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Ap stars whose spectral lines are resolved in several magnetically split components are of particular interest, because their magnetic field can be diagnosed with unrivalled precision, in an essentially approximation-free manner. We are pursuing a systematic programme of search and study of such stars. At present 25 of them are known, of which 13 have been discovered in the course of the present project (Mathys 1990, hereafter Paper I; Mathys & Lanz 1992, hereafter Paper II; this paper).

Up to now, we have obtained observations of 22 of these Ap stars with resolved magnetically split lines. We have recorded high-resolution spectra of a region containing, among others, the three lines Cr ɪɪ λ6147.154, Fe ɪ λ6147.741, and Fe II λ 6149.258. The Zeeman patterns of these three lines are, respectively, close to a triplet, close to a quadruplet, and a doublet. The doublet Fe ɪɪ λ 6149.258 is particularly interesting, because of its large Landé factor (2.7): it can be resolved even in stars with fairly modest fields.

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. 300 - 304
Copyright
Copyright © Astronomical Society of the Pacific 1993

Footnotes

*

Based on observations collected at the European Southern Observatory, La Silla, Chile, and at the Observatoire de Haute-Provence, Saint-Michell’Observatoire, France

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