HD 96446: a puzzle for current models of magnetospheres?
Abstract
Context. Oblique magnetic dipole fields have been detected in Bp stars for several decades, and more recently also in normal massive stars. In the past decade, it has been established that stellar magnetospheres form through the channelling and confinement of an outflowing stellar wind by the stellar magnetic field. This explains specific properties of magnetic massive stars, such as their rotationally modulated photometric light curve, Hα emission, UV spectra, and X-ray emission.
Aims: In the framework of the MiMeS (Magnetism in Massive Stars) project, four HARPSpol observations of the magnetic Bp star
Methods: We first updated the basic parameters of
Results: We find radial velocity variations with a period around 2.23 h, that we attribute to β Cep-type p-mode pulsations. We detect clear direct magnetic Stokes V signatures with slightly varying values of the longitudinal magnetic field, typical of an oblique dipole rotator, and show that these signatures are not much perturbed by the radial velocity variations. The magnetic confinement parameter and Alfvén radius in the centrifugally supported, rigidly-rotating magnetosphere (CM) model points towards the presence of confined material in the magnetosphere. However,
Conclusions: We conclude that, even though
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- October 2012
- DOI:
- 10.1051/0004-6361/201218988
- Bibcode:
- 2012A&A...546A..44N
- Keywords:
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- stars: magnetic field;
- stars: early-type;
- stars: individual: HD 96446;
- stars: fundamental parameters;
- stars: abundances;
- stars: winds;
- outflows