Unveiling the Cygnus OB2 stellar population with Chandra J. F. Albacete Colombo, E. Flaccomio, G. Micela, S. Sciortino and F. Damiani A&A, 464 1 (2007) 211-227 Published online: 20 November 2006 DOI: 10.1051/0004-6361:20066101