Rapidly evolving circularly polarized emission during the 1994 outburst of GRO J1655–40 J.-P. Macquart, K. Wu, R. J. Sault and D. C. Hannikainen A&A, 396 2 (2002) 615-621 Published online: 03 December 2002 DOI: 10.1051/0004-6361:20021428