Magnetic field measurements of ϵ Eridani from Zeeman broadening     

L. T. Lehmann  A. Künstler  T. A. Carroll  K. G. Strassmeier 《Astronomische Nachrichten》2015,336(3):258-265

We present new magnetic field measurements of the K2 main‐sequence star ϵ Eri 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 échelle 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 tobe 〈B〉 = 186 ± 47 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 ϵ Eri. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献