Today's Colloquium: The quest for particle-accelerating colliding-wind binaries across the electromagnetic spectrum

© Micha�l de Becker

Massive stars are extreme stellar objects whose properties allow for the study of some interesting physical processes, including particle acceleration up to relativistic velocities. In particular, the collisions of massive star winds in binary systems are adequate environments to accelerate notably electrons involved in synchrotron emission. This leads to their identification as non-thermal radio emitters. To date, this has been demonstrated for about 40 objects.

The relativistic electrons are also expected to produce non-thermal high-energy radiation through inverse Compton scattering. This class of objects permits thus to investigate non-thermal physics through observations in the radio and high energy spectral domains. However, the binary nature of these sources introduces some stringent requirements to adequately interpret their behavior and model non-thermal processes. In particular, these objects are well-established variable stellar sources on the orbital time-scale. The stellar and orbital parameters need to be determined, and this is notably achieved through studies in the optical domain.

The combination of observations in various spectral domains is thus the key to investigate these particle-accelerating colliding-wind binaries, and achieve a clearer view of their role in stellar and galactic astrophysics.