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Zeeman-Doppler imaging of II Peg

Published online by Cambridge University Press:  01 November 2008

Thorsten A. Carroll ,
Markus Kopf ,
Klaus G. Strassmeier ,
Ilya Ilyin  and
Ilkka Tuominen
Thorsten A. Carroll
Affiliation:
Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14882 Potsdam, Germany email: tcarroll@aip.de
Markus Kopf
Affiliation:
Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14882 Potsdam, Germany email: tcarroll@aip.de
Klaus G. Strassmeier
Affiliation:
Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14882 Potsdam, Germany email: tcarroll@aip.de
Ilya Ilyin
Affiliation:
Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14882 Potsdam, Germany email: tcarroll@aip.de
Ilkka Tuominen
Affiliation:
Observatory, University of Helsinki, PO Box 14, FI-00014 Helsinki, Finland
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Abstract

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We present Zeeman-Doppler images of the active K2 star II Peg for the years 2004 and 2007. The surface magnetic field was reconstructed with our new ZDI code iMap which provides a full polarized radiative transfer driven inversion to simultaneously reconstruct the surface temperature and magnetic vector field distribution. II Peg shows a remarkable large scale magnetic field structure for both years. The magnetic field is predominantly located at high latitudes and is arranged in active longitudes. A dramatic evolution in the magnetic field structure is visible for the two years, where a dominant and largely unipolar field in 2004 has changed into two distinct and large scale bipolar structures in 2007.

Keywords

Stars: activity – stars: magnetic fields – stars: spots – radiative transfer – methods: data analysis

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