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Paper: EK Eri: Magnetic Topology and Rotational Period
Volume: 448, 16th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun
Page: 1065
Authors: Aurière, M.; Konstantinova-Antova, R.; Petit, P.; Roudier, T.
Abstract: We have observed during 3 seasons the slow rotating but active G8 giant EK Eri with the new generation spectropolarimeter NARVAL at Telescope Bernard Lyot (Observatoire du Pic du Midi, France). We got 21 observations between 20 September 2007 and 22 March 2010. For all the spectra, we detected a significant Zeeman Stokes V signature and the corresponding surface-averaged longitudinal magnetic field varies between -13 G and -98 G, without reversing its sign. We fitted the Stokes V profiles with a model of large-scale magnetic field and obtained a Zeeman Doppler image of it. Our best fitted model gives a rotational period of about 300 days. A strong magnetic spot dominates the visible surface magnetic field and is phased with the photometric spot given by the ephemeris of Dall et al. (2010). Whereas a quadripolar component dominates for i greater than 80°, for i= 60°, we get a model almost purely dipolar. In the dipolar model, the strong magnetic/photometric spot would correspond to the pole of negative polarity of the dipole, which could be the remnant of that of the Ap star progenitor of EK Eri.
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