Hot C-rich white dwarfs: testing the DB–DQ transition through pulsations A. H. Córsico, A. D. Romero, L. G. Althaus and E. García-Berro A&A, 506 2 (2009) 835-843 Published online: 27 August 2009 DOI: 10.1051/0004-6361/200912481