2002A&A...385..619V

Photometric and spectroscopic monitoring campaigns of WR46 (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_sw⁸⁹=0.1412d in 1989, and P_sw⁹¹=0.1363d in 1991. Because of a small difference in the minima, this periodicity may be a double-wave phenomenon (P_dw). 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 0.12mag appeared to accompany the period change. In addition, the light variations in 1989 show strong evidence for an additional period P_x=0.2304d. 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. (2000AJ....120.2101M). 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 WR46 may be solved.