The 17-d periodicity of Cygnus X-3

The results of digitization and power-spectrum analysis of the primary data of Ariel V observations of the flux variations of Cygnus X-3, first reported by Holt et al. (1976), indicate that there is about 50% likelihood that there exists a 16.75-day periodicity, as suggested in the first report. In an accompanying reply, Holt concurs that the 16.75-day periodicity may be artifactual, but emphasizes that the possible periodicity was mentioned because the same effect was present in the Ariel V Sky Survey Experimental data, which constitute a completely independent set of data.