1998A&A...332..605S

In this paper we discuss the light variations of HD 163868 on the basis of all available photometric data originating from photometric monitoring during the last two decades. We suggest that one explanation of the on-and-off type variability can be a binary configuration with a compact companion and a period of the order of 850 days, though the observed effects could also be seen in the context of positive interference of NRPs. The bright stages are associated with strong reddening consistent with an increase in circumstellar material. We draw the attention to the similarity with cyclically-recurrent mild S Dor phases of LBVs.