Evidence for a sharp structure variation inside a red-giant star A. Miglio, J. Montalbán, F. Carrier, J. De Ridder, B. Mosser, P. Eggenberger, R. Scuflaire, P. Ventura, F. D'Antona, A. Noels and A. Baglin A&A, 520 (2010) L6 Published online: 28 September 2010 DOI: 10.1051/0004-6361/201015442