Vol. 550
In section 7. Stellar structure and evolution

Magnetic field topology of the RS CVn star II Pegasi

by O. Kochukhov, M.J. Mantere, T. Hackman, and I. Ilyin A&A 550, A84


The authors follow the long-term evolution of the magnetic field topology of the RS CVn binary star II Peg using an elaborate Zeeman-Doppler imaging approach and high-resolution circular polarization observations from the SOFIN spectropolarimeter at the Nordic Optical Telescope, covering 12 epochs spread over 7 years. They detect clear magnetic field signatures in average Stokes V profiles for all 12 data sets, corresponding to mean longitudinal fields of 50­-100 G. Magnetic inversions reveal evolving magnetic fields with typical local strengths of 0.5­-1.0 kG and complex topologies. The results suggest that the magnetic field is produced mainly by the turbulent alpha^2 dynamo rather than the solar alpha-omega dynamo.