The absence of a short period in the WN5 star EZ Canis Majoris

Abstract

Several suggestion have been put forward to explain the 3.d766 periodicity of EZ CMa (WR6): (i) WR+c system; (ii) rotating single WR star; (iii) pulsations (non—radial (NRP) or radial) with frequency reduced by some kind of filtering in the wind. In this paper, we report on a photometric investigation based on a long continuous observing run, in an attempt to verify whether EZ CMa does in fact show a unique periodicity. In particular, this work was motivated by the claim by Gosset & Vreux (1987), based on the data from Lamontagne et al. (1986, hereafter LML), that EZ CMa may have a shorter period besides the one at 3.d766, a frequency close to but not equal to the third harmonic of the 3.d766 period.