The magnetic field of Betelgeuse: a local dynamo from giant convection cells? (original) (raw)
ADS
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Abstract
Context. Betelgeuse is an M supergiant with a complex and extended atmosphere, which also harbors spots and giant granules at its surface. A possible magnetic field could contribute to the mass loss and to the heating of the outer atmosphere.
Aims: We observed Betelgeuse, to directly study and infer the nature of its magnetic field.
Methods: We used the new-generation spectropolarimeter NARVAL and the least square deconvolution (LSD) method to detect circular polarization within the photospheric absorption lines of Betelgeuse.
Results: We have unambiguously detected a weak Stokes V signal in the spectral lines of Betelgeuse, and measured the related surface-averaged longitudinal magnetic field B_ℓ at 6 different epochs over one month. The detected longitudinal field is about one Gauss and is apparently increasing on the time scale of our observations.
Conclusions: This work presents the first direct detection of the magnetic field of Betelgeuse. This magnetic field may be associated to the giant convection cells that could enable a “local dynamo”.
Based on observations obtained at the Télescope Bernard Lyot (TBL) at Observatoire du Pic du Midi, CNRS/INSU and Université de Toulouse, France.
Publication:
Astronomy and Astrophysics
Pub Date:
June 2010
DOI:
arXiv:
Bibcode:
Keywords:
- stars: individual: Betelgeuse;
- stars: magnetic field;
- stars: late-type;
- supergiants;
- Astrophysics - Solar and Stellar Astrophysics
E-Print:
Accepted as a letter for A&