| Abstract
| - Photometric and spectroscopic monitoring campaigns of WR 46 (WN3p), as presented in Veen et al. (2002a,b; hereafter Papers I and II, respectively), yield the following results. The light- and colour variations reveal a dominant single-wave period of $P_{\rm sw}^{89}=0.1412$ d in 1989, and $P_{\rm sw}^{91}=0.1363$ d in 1991. Because of a small difference in the minima, this periodicity may be a double-wave phenomenon ( Pdw). The line fluxes vary in concert with the magnitudes. The significant difference of the periods can be either due to the occurence of two distinct periods, or due to a gradual change of the periodicity. A gradual brightening of the system of 0 $\fm$12 appeared to accompany the period change. In addition, the light variations in 1989 show strong evidence for an additional period $P_{\rm x}=0.2304$ d. Generally, the radial velocities show a cyclic variability on a time scale of the photometric double-wave. However, often they do not vary at all. The observed variability confirms the Population I WR nature of the light source, as noted independently by Marchenko et al. (2000). In the present paper, we first show how the photometric double-wave variability can be interpreted as a rotating ellipsoidal density distribution in the stellar wind. Subsequently, we discuss what mechanisms could drive such a configuration. First, stellar rotation of a single star is discarded as a likely cause. Second, the obvious interpretation of the double-wave photometry, i.e., a close binary system, is investigated. However unlikely, we discuss how the observed period change might be reconciled within a model of a strongly interacting binary. Third, an interpretation of a non-radial multi-mode pulsator is investigated. The observed period change and the multi-frequency behaviour do support this interpretation. We propose that the pulsational mode $l=1$ and $|m|=1$ may mimic a “binary” light- and radial-velocity curve. However, the phasing of the radial velocity and the light curve may be inconsistent. The possibility $l=2$ and $|m|=0$ is also discussed. Finally, we suggest how the enigma of the variability of WR 46 may be solved.
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