An investigation of the large-scale variability of the apparently single Wolf-Rayet star WR 1

In recent years, much studies have focused on determining the origin of the large-scale line-profile and/or photometric patterns of variability displa yed by some apparently single Wolf-Rayet stars, with the existence of an un seen (collapsed?) companion or of spatially extended wind structures as pot ential candidates. We present observations of WR 1 which highlight the unus ual character of the variations in this object. Our narrowband photometric observations reveal a gradual increase of the stellar continuum flux amount ing to Delta v approximate to 0.09 mag followed by a decline on about the s ame timescale (3-4 days). Only marginal evidence for variability is found d uring the 11 following nights. Strong, daily line-profile variations are al so observed but they cannot be easily linked to the photometric variations. Similarly to the continuum flux variations, coherent time-dependent change s are observed in 1996 in the centroid, equivalent width, and skewness of H e II lambda 4686. Despite the generally coherent nature of the variations, we do not find evidence in our data for the periods claimed in previous stu dies. While the issue of a cyclical pattern of variability in WR 1 is still controversial, it is clear that this object might constitute in the future a cornerstone for our understanding of the mechanisms leading to the forma tion of largely anisotropic outflows in Wolf-Rayet stars.