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S.L. Skinner (JILA / Univ. of Colorado), M. Itoh (Kobe University), F. Nagase (Inst. of Space and Astronautical Science (ISAS)), S.A. Zhekov (JILA / Univ. of Colorado)
We present new X-ray and radio observations of the unusual Wolf-Rayet (WR) star WR 147 (=AS 431) obtained {\em simultaneously} with ASCA and the VLA. The VLA data are unique amongst WR stars, consisting of near-simultaneous observations at five different wavelengths. Previous observations suggest that WR 147 is a massive WR + OB binary system, and we thus compare the new data with predictions from colliding wind shock models using both analytic methods and hydrodynamic simulations. The X-ray temperature structure is consistent with colliding wind predictions, but the X-ray absorption is much larger than expected from the winds alone and the X-ray luminosity is lower than predicted. We discuss possible reasons for these differences. We confirm that the radio emission consists of a thermal free-free component from the ionized WR wind and a nonthermal component. But, a new finding is that conventional power-law and self-absorbed synchrotron models cannot explain the nonthermal radio emission. This result is unexpected if the nonthermal emission is due to relativistic electrons accelerated via the Fermi mechanism in a colliding wind shock. We discuss alternative nonthermal emission models which can accurately reproduce the VLA data.
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