Physical Sciences: Short-term Periodic Variations following an Optical Flare of Sco X-1

Abstract

WE have recently carried out a detailed investigation of the “flickering” of the optical source associated with Sco X-1 using the technique of power spectrum analysis to search for periodicities in the photometric data of Sandage et al.¹. In common with others^2,3, we have found no evidence for stable periodic structure when the time series resulting from a whole night's observations is analysed. But we have also studied shorter stretches of data (500 to 900 consecutive data points) chosen so that no large-scale flaring occurred during these periods. Many of these short runs seem to contain periodic structure at one or more frequencies, corresponding to components with amplitudes in the range 0.1 to 0.5 per cent of the mean intensity over the appropriate interval. The results of this work (unpublished) have encouraged us to look more closely at certain regions of the data.