Magnetic field and convection in the cool supergiant Betelgeuse

• Main Authors: Petit, P., Aurière, M., Konstantinova-Antova, R., Morgenthaler, A., Perrin, G., Roudier, T., Donati, J. -F.
• Format: Text
• Language: unknown
• Published: arXiv 2011
• Subjects: Solar and Stellar Astrophysics astro-ph.SR; FOS Physical sciences; narval
• Online Access: https://dx.doi.org/10.48550/arxiv.1109.3979; https://arxiv.org/abs/1109.3979

We present the outcome of a highly-sensitive search for magnetic fields on the cool supergiant Betelgeuse. A time-series of six circularly-polarized spectra was obtained using the NARVAL spectropolarimeter at Télescope Bernard Lyot (Pic du Midi Observatory), between 2010 March and April. Zeeman signatures were repeatedly detected in cross-correlation profiles, corresponding to a longitudinal component of about 1 G. The time-series unveils a smooth increase of the longitudinal field from 0.5 to 1.5 G, correlated with radial velocity fluctuations. We observe a strong asymmetry of Stokes V signatures, also varying in correlation with the radial velocity. The Stokes V line profiles are red-shifted by about 9 km/s with respect to the Stokes I profiles, suggesting that the observed magnetic elements may be concentrated in the sinking components of the convective flows. : Submitted to Lecture Notes in Physics (CNRS astronomy school : "From solar environment to stellar environment")