THE NATURE OF THE CM-MM EMISSION IN CLOSE WOLF-RAYET BINARIES

The centimeter spectra of Wolf-Rayet (WR) binaries often show a contribution from a wind-wind collision region (WCR) between the stars. In short period systems (less than or similar to 1 yr), such a component is expected to be absorbed by the unshocked winds, losing any effect from its binarity. Recent studies suggest that the WCR in these systems may also contribute to the emission at both centimeter and millimeter wavelengths. We analyzed and compared centimeter and millimeter observations of a total sample of 17 WR stars (including nine confirmed short-period systems) to detect any possible WCR contribution. More detailed observations are required in order to distinguish between different scenarios. We highlight the importance of analyzing the spectrum from quasi-simultaneous observations in a wide range of frequencies in order to properly characterize and distinguish any possible extra contribution.