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Modeling Oblique Rotators: Magnetospheres and Winds

Published online by Cambridge University Press:  12 April 2016

Steven N. Shore*
Affiliation:
Department of Physics and Astronomy, Indiana University South Bend, 1700 Mishawaka Ave., South Bend, IN 46634-7111USA

Abstract

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The upper main sequence chemically peculiar (CP) stars display evidence of trapped circumstellar gas and nonspherical outflows. These stars are also known to possess strong magnetic fields that are often highly inclined to the rotational axis. Their phenomenology can be understood by using the oblique rotator model, which has successfully accounted for the observed behavior of the cooler CP stars. This paper reviews some features of the oblique rotator model, in which the magnetic field is assumed to provide a rigid framework for the structuring of the stellar and circumstellar gas. Corotation of circumstellar plasma is enforced out to the Alfven radius in the magnetic equatorial plane, while for the hotter stars, a radiatively driven wind emerges from the magnetic polar caps. Some observable consequences of the model are discussed, especially the Hα and ultraviolet resonance line absorption and emission periodic variability that has been observed in the He-peculiar stars and nonthermal radio emission. Magnetospheres may also be present in O stars, e.g. θ1 Ori C, and in the Herbig Ae/Be stars.

Type
Section II Theory of Non-spherical Winds
Copyright
Copyright © Springer-Verlag 1999

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