Variable X-ray emission from the accretion shock in the classical T Tauri star V2129 Ophiuchi C. Argiroffi, E. Flaccomio, J. Bouvier, J.-F. Donati, K. V. Getman, S. G. Gregory, G. A. J. Hussain, M. M. Jardine, M. B. Skelly and F. M. Walter A&A, 530 (2011) A1 Published online: 27 April 2011 DOI: 10.1051/0004-6361/201016321