2818 20160701171711.0 10.1017/S1743921311011689 DOI ASTROimport-975 Volpi, D. 2011 Non-thermal radio emission from colliding-wind binaries: modelling Cyg OB2 No. 8A and No. 9 Some OB stars show variable non-thermal radio emission. The non-thermal emission is due to synchrotron radiation that is emitted by electrons accelerated to high energies. The electron acceleration occurs at strong shocks created by the collision of radiatively-driven stellar winds in binary systems. Here we present results of our modelling of two colliding wind systems: Cyg OB2 No. 8A and Cyg OB2 No. 9. Blomme, R. De Becker, M. Rauw, G. Active OB Stars: Structure, Evolution, Mass Loss, and Critical Limits 272 2011 638-639 http://esoads.eso.org/abs/2011IAUS..272..638V published in NONREF