1996A&A...313..537B

We report the result of the 3 year search for rapid oscillation of WR stars predicted by stellar models (Schaller 1992, Glatzel et al. 1993). The photometry of 6 WR stars (4 WN and 2 WC stars) was carried out during the best photometric nights in 9 runs of 3 weeks using the multi-channel photometer mode of the CCD camera attached to the 0.7m Swiss telescope at La Silla ESO observatory. One 5-day simultaneous spectroscopic (1.52m ESO telescope) and photometric run has also been included. We confirm the detection of the oscillation by Matthews et al. (1992) for WR6 (HD 50896) and we made two unconfirmed new detections (for WR78 and WR111). Nevertheless and taking into account the scarcity of the event and the difficulties to observe it, such oscillations remain to be confirmed in a more reliable way. We set the upper limit to the amplitude of such oscillations in shot-noise limited observing conditions to 1.15mmag in all UBV filters. No variation of emission lines was detected in moderate resolution spectra. We do not confirm the first detection of a 627 sec period oscillation of WR40 reported by Blecha et al. (1992).