Magnetic field topology of the RS CVn star II Pegasi

摘要: Context. The dynamo processes in cool active stars generate complex magnetic fields responsible for prominent surface stellar activity and variability at different time scales. For a small number of field topologies were reconstructed from the series spectropolarimetric observations using Zeeman Doppler imaging (ZDI) method, often yielding surprising controversial results. Aims. In this study we follow long-term evolution topology RS CVn binary star II Peg more self-consistent physically meaningful modelling approach compared to previous ZDI studies. Methods. We collected high-resolution circular polarisation SOFIN spectropolarimeter Nordic Optical Telescope. These data cover 12 epochs spread over 7 years, comprising one most comprehensive sets acquired star. A multi-line diagnostic technique combination with new code is applied interpret these observations. Results. have succeeded detecting clear signatures average Stokes V profiles all sets. typically shapes amplitudes similar 10(-3) unpolarised continuum, corresponding mean longitudinal 50-100 G. Magnetic inversions reveals evolving typical local strengths 0.5-1.0 kG topologies. Despite temperature mapping technique, do not find correlation between features maps. Neither confirm presence persistent azimuthal rings found other stars. Reconstruction significant both structure extended magnetospheric geometry on scale covered by our From 2004 2010 total energy drastically declined became less axisymmetric. This also coincided transition predominantly poloidal mainly toroidal topology. Conclusions. qualitative comparison maps prediction theory suggests that produced turbulent alpha(2) rather than solar alpha Omega dynamo. Our results show longitude system, nor there evidence an wave.