Magnetic field topology of the RS CVn star II Pegasi

: Kochukhov O, Mantere MJ, Hackman T, Ilyin I

: 2013

Astronomy and Astrophysics

: ASTRONOMY & ASTROPHYSICS

: ASTRON ASTROPHYS

: ARTN A84

: 550

: A84

: 19

: 0004-6361

DOI: https://doi.org/10.1051/0004-6361/201220432

Context. The dynamo processes in cool active stars generate complex magnetic fields responsible for prominent surface stellar
activity and variability at dierent time scales. For a small number of cool stars magnetic field topologies were reconstructed from
the time series of spectropolarimetric observations using the Zeeman Doppler imaging (ZDI) method, often yielding surprising and
controversial results.
Aims. In this study we follow a long-term evolution of the magnetic field topology of the RS CVn binary star II Peg using a more
self-consistent and physically more meaningful modelling approach compared to previous ZDI studies.
Methods. We collected high-resolution circular polarisation observations of II Peg using the SOFIN spectropolarimeter at the Nordic
Optical Telescope. These data cover 12 epochs spread over 7 years, comprising one of the most comprehensive spectropolarimetric
data sets acquired for a cool active star. A multi-line diagnostic technique in combination with a new ZDI code is applied to