We propose to spectroscopically monitor over four full uninterrupted months a key single star showing clear signs of each type of structure: WR135 for clumps and WR134 & WR 137 for CIR.
WR135 is the best case known for clarity of clumping (Lepine et al. 2000, AJ, 120, 3201), while not revealing any clear signature of CIRs so far.
WR134 is one of the two WR stars showing the clearest CIRs (rotating in a period of P = 2.27d) , along with WR6 (P = 3.77d). (Only three WR stars have known CIR periodicities so far, WR 1, 6 and 134.) As with all WR stars, the wind of WR134 also shows clumping. However, WR134 has the shortest known period, making it the fastest known rotating WR star. This will prove useful when it comes to verifying over a four-month interval how stable the CIR features are over many rotation cycles.
WR137 has an even shorter suspected CIR period, P = 0.84d (Lefevre et al. 2005, MNRAS, 360, 141), but which needs to be confirmed and examined in detail.
All stars lie within a half a degree of each other on the sky, so can be alternately observed conveniently together high in the sky for most of the summer nights in the northern hemisphere from June through September. We suggest the summer of 2013, allowing us enough time to properly organize the campaign.
Upper panel: observations of CIR (phased in P = 2.27 d) in WR134 (Morel et al. 1999, ApJ, 518, 428: Fig. 4 for HeII 4686). The next panel shows all profiles of HeII 4686 superposed, while the bottom panel shows the Temporal Variance Spectrum (thin solid line) used to evaluate the significance of variability (dashed horizontal line for 99.0% confidence level; the thick line is the mean spectrum). Although these data look quite complete, a much more intense campaign is needed to fill the gaps and verify how the CIRs have evolved.