- Search for surface magnetic fields in Mira stars: first results on χ Cyg doi link

Auteur(s): Lebre A., Aurière Michel, Fabas N., Gillet Denis, Herpin Fabrice, Petit Pascal, Konstantinova-Antova Renada

Conference: Magnetic Fields throughout Stellar Evolution (Biarritz, FR, 2013)
Actes de conférence: Magnetic Fields throughout Stellar Evolution, Proceedings of the International Astronomical Union, , IAU Symposium, Volume 302, pp. 385-388 - 2014 - held 30 august 2013 - Biaritz - France -2014IAUS..302..385L, vol. 302 p.385-388 (2014)

Ref HAL: hal-01061808_v1
DOI: 10.1017/S1743921314002579
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So far, surface magnetic fields have never been reported on Mira stars, while observational facilities allowing detection and measurement of weak surface fields through the Zeeman effect have become available. Then, in order to complete the knowledge of the magnetic field and of its influence during the transition from Asymptotic Giant Branch (AGB) to Planetary Nebulae (PN) stages, we have undertaken a search for magnetic fields at the surface of Miras. We present the first spectropolarimetric observations (performed with the Narval instrument at Télescope Bernard Lyot-TBL, Pic du Midi, France) of the S-type Mira star χ Cyg. We have detected a polarimetric signal in the Stokes V spectra and we have established its Zeeman origin. We claim that it is likely to be related to a weak magnetic field present at the photospheric level and in the lower part of the stellar atmosphere. The origin of this magnetic field is discussed in the framework of shock waves periodically propagating throughout the atmosphere of a Mira.