New type of brightness variations of the colliding wind WO4 + O5((f)) binary WR 30a S. J. Paardekooper, K. A. van der Hucht, A. M. van Genderen, E. Brogt, M. Gieles and R. Meijerink A&A, 404 2 (2003) L29-L32 Published online: 02 June 2003 DOI: 10.1051/0004-6361:20030574