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We present the results of a four-month, spectroscopic campaign of theWolf-Rayet dust-making binary, WR137. We detect only small-amplitude, randomvariability in the CIII5696 emission line and its integrated quantities (radialvelocity, equivalent width, skewness, kurtosis) that can be explained bystochastic clumps in the wind of the WC star. We find no evidence oflarge-scale, periodic variations often associated with Corotating InteractionRegions that could have explained the observed intrinsic continuum polarizationof this star. Our moderately high-resolution and high signal-to-noise averageKeck spectrum shows narrow double-peak emission profiles in the Halpha, Hbeta,Hgamma, HeII6678 and HeII5876 lines. These peaks have a stable blue-to-redintensity ratio with a mean of 0.997 and a root-mean-square of 0.004,commensurate with the noise level; no variability is found during the entireobserving period. We suggest that these profiles arise in a decretion diskaround the O9 companion, which is thus an O9e star. The characteristics of theprofiles are compatible with those of other Be/Oe stars. The presence of thisdisk can explain the constant component of the continuum polarization of thissystem, for which the angle is perpendicular to the plane of the orbit,implying that the rotation axis of the O9e star is aligned with that of theorbit. It remains to be explained why the disk is so stable within the strongultraviolet radiation field of the O star. We present a binary evolutionaryscenario that is compatible with the current stellar and system parameters.

An extensive spectroscopic time series of three Wolf-Rayet stars -- II. A search for wind asymmetries in the dust-forming WC7 binary WR137