Magnetic field measurements of $\epsilon$ Eridani from Zeeman broadening

Abstract

We present new magnetic field measurements of the K2 main-sequence star $\epsilon$ Eridani based on principal components analysis (PCA) line-profile reconstructions. The aim of this paper is to quantify the surface-averaged magnetic field and search for possible variations. A total of 338 optical echelle spectra from our robotic telescope facility STELLA with a spectral resolution of 55,000 were available for analysis. This time-series was used to search for the small line-profile variations due to a surface magnetic field with the help of a PCA. Evidence for a spatial and temporal inhomogeneous magnetic field distribution is presented. The mean, surface averaged, magnetic field strength was found to be $⟨B⟩=186\pm 47\mathrm{G}$ in good agreement with previous Zeeman-broadening measurements. Clear short-term variations of the surface averaged magnetic field of up to few tens Gauss were detected together with evidence for a three-year cycle in the surface-averaged magnetic field of $\epsilon$ Eridani.

References in corpus (5)

• The Extrasolar Planet epsilon Eridani b - Orbit and Mass
• Magnetic Activity Cycles in the Exoplanet Host Star epsilon Eridani
• The differential rotation of epsilon Eri from MOST data
• Three years of experience with the STELLA robotic observatory
• Zeeman-Doppler Imaging : Old Problems and New Methods

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• Diagnosing large-scale stellar magnetic fields using PCA on spectropolarimetric data
• Stellar Cycles in Fully Convective Stars and a New Interpretation of Dynamo Evolution
• Coronal mass ejections and type II radio emission variability during a magnetic cycle on the solar-type star $\epsilon$ Eridani
• Unsigned magnetic flux proxy from solar optical intensity spectra
• Detection of 2$-$4 GHz Continuum Emission from $\epsilon$ Eridani
• The energy budget of stellar magnetic fields: comparing non-potential simulations and observations
• The multi-line slope method for the measure of the effective magnetic field of the cool stars: an application to the solar like cycle of ε Eri
• An application of a solar-type dynamo model for Epsilon Eridani
• Comparison of solar multifrequency microwave data with other solar indices for understanding solar and stellar microwave data