VLA Observations of the Interacting‐Wind Binary System WR 147

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Abstract
Wolf-Rayet stars are losing mass via their strong winds. Some of them show thermal and nonthermal radio emission, and from this group, some have companions that are forming binary systems. It has been suggested that the synchrotron emission arises from the interaction region where the winds of the two stars collide. WR 147 seems to be one of these systems, having a companion and emitting thermal as well as nonthermal radiation. Besides, it has been suggested that it has an anisotropic wind. In this work, we present VLA observations that provide new information on this system. The thermal main component (WR 147S) shows a flux density increase of ~25% from 1995 to 1996. This could be due to a change in the wind parameters. The nonthermal wind-interaction zone (WR 147N) remained constant in flux. To first approximation, our maps are consistent with an isotropic wind from WR 147S. However, our results show possible faint condensations in the wind that have moved away by ~02 from WR 147S in a time interval of ~1.4 yr. This fact seems to indicate that we are dealing with an inhomogeneous wind. Finally, in a qualitative manner, the morphology of WR 147N resembles a shock like those modeled theoretically for interacting winds. In order to have a more quantitative description of the shock, we have fitted a curve that follows adequately the observed shape. This curve was obtained by fixing the ratio of momenta between the interacting stellar winds. In this way, we have derived a range of possible inclination angles of the system (45° ± 15°) by projecting the theoretical curve onto the plane of the sky. Thus, our results give further support to the interpretation of WR 147 as an interacting-wind binary system.