X-Ray and Optical Observations of Sco X-1

Abstract

We report on a number of Copernicus observations of Sco X-1, in both its quiescent and active states, made between 1973 and 1975. The active states consisted of flaring intervals lasting several hours, made up of series of bursts with duration 4–15 min, and involving intensity increases up to almost twice the non-flaring level. Temperatures during this state ranged from 5.5 to > 20 keV and were well correlated with the intensity level. During quiescent states the source exhibited 20 per cent flux variability over several hours, with a lower emission measure and higher temperature than at the corresponding flux level in the active state. During active states the minimum source intensity (between flares) has the same value in all observations some of which were separately by up to 2 years. In quiescent periods the intensity was never below this minimum. These data are discussed and compared with the results of previous observers. Some optical photometric and spectroscopic results obtained simultaneously with a Copernicus observation are also presented.