Mon. Not. R. Astron. Soc., 423, 1562-1570 (2012/June-3)
MHD numerical simulations of colliding winds in massive binary systems – I. Thermal versus non-thermal radio emission.
FALCETA-GONCALVES D. and ABRAHAM Z.
Abstract (from CDS):
In the past few decades detailed observations of radio and X-ray emission from massive binary systems revealed a whole new physics present in such systems. Both thermal and non-thermal components of this emission indicate that most of the radiation at these bands originates in shocks. O and B-type stars and Wolf–Rayet (WR) stars present supersonic and massive winds that, when colliding, emit largely due to the free–free radiation. The non-thermal radio and X-ray emissions are due to synchrotron and inverse Compton processes, respectively. In this case, magnetic fields are expected to play an important role in the emission distribution. In the past few years the modelling of the free–free and synchrotron emissions from massive binary systems have been based on purely hydrodynamical simulations, and ad hoc assumptions regarding the distribution of magnetic energy and the field geometry. In this work we provide the first full magnetohydrodynamic numerical simulations of wind–wind collision in massive binary systems. We study the free–free emission characterizing its dependence on the stellar and orbital parameters. We also study self-consistently the evolution of the magnetic field at the shock region, obtaining also the synchrotron energy distribution integrated along different lines of sight. We show that the magnetic field in the shocks is larger than that obtained when the proportionality between B and the plasma density is assumed. Also, we show that the role of the synchrotron emission relative to the total radio emission has been underestimated.
2012 The Authors Monthly Notices of the Royal Astronomical Society2012 RAS