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2008MNRAS.389...75B - Mon. Not. R. Astron. Soc., 389, 75-85 (2008/September-1)
The weak magnetic field of the O9.7 supergiant ζ Orionis A.
BOURET J.-C., DONATI J.-F., MARTINS F., ESCOLANO C., MARCOLINO W., LANZ T. and HOWARTH I.D.
Abstract (from CDS):
The magnetic topology of ζOriA is apparently more complex than a dipole and involves two main magnetic polarities located on both sides of the same hemisphere; our data also suggest that ζOriA rotates in about 7.0d and is about 40° away from pole-on to an Earth-based observer. Despite its weakness, the detected magnetic field significantly affects the wind structure; the corresponding Alfvén radius is however very close to the surface, thus generating a different rotational modulation in wind lines than that reported on the two other known magnetic O stars.
The rapid rotation of ζOriA with respect to θ1OriC appears as a surprise, both stars having similar unsigned magnetic fluxes (once rescaled to the same radius); it may suggest that the subequipartition field detected on ζOriA is not a fossil remnant (as opposed to that of θ1 OriC and HD191612), but the result of an exotic dynamo action produced through magnetohydrodynamics (MHD) instabilities.
Abstract Copyright: © 2008 The Authors. Journal compilation © 2008 RAS
Journal keyword(s): stars: early-type - stars: individual: ζOriA - stars: magnetic fields - stars: rotation - stars: winds, outflows
Simbad objects: 7
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