High-resolution spectro-polarimetry of a flaring sunspot penumbra J. Hirzberger, T. Riethmüller, A. Lagg, S. K. Solanki and P. Kobel A&A, 505 2 (2009) 771-790 Published online: 22 July 2009 DOI: 10.1051/0004-6361/200912063