Proceedings of the International Astronomical Union

Contributed Papers

Non-thermal radio emission from colliding-wind binaries: modelling Cyg OB2 No. 8A and No. 9

Delia Volpia1, Ronny Blommea1, Michael De Beckera2a3 and Gregor Rauwa2

a1 Royal Observatory of Belgium, Ringlaan 3, B-1180 Brussels, Belgium, email:

a2 Institut d'Astrophysique, Université de Liège, Allée du 6 Août, 17, Bât B5c, B-4000 Liège (Sart-Tilman), Belgium

a3 Observatoire de Haute-Provence, F-04870 Saint-Michel l'Observatoire, France


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.


  • plasmas;
  • radiation mechanisms: nonthermal;
  • methods: numerical;
  • binaries: spectroscopic;
  • stars: early-type;
  • stars: winds;
  • outflows