The corona and companion of CoRoT-2a. Insights from X-rays and optical spectroscopy S. Schröter, S. Czesla, U. Wolter, H. M. Müller, K. F. Huber and J. H. M. M. Schmitt A&A, 532 (2011) A3 Published online: 11 July 2011 DOI: 10.1051/0004-6361/201116961