Lyot-plane phase masks for improved high-contrast imaging with a vortex coronagraph G. J. Ruane, E. Huby, O. Absil, D. Mawet, C. Delacroix, B. Carlomagno and G. A. Swartzlander Jr. A&A, 583 (2015) A81 Published online: 30 October 2015 DOI: 10.1051/0004-6361/201526561