Abstract
THE collimated proportional counter (experiment C of MSSL) on Ariel V viewed Cyg X-1 in 1975 from May 3 1400 UT until May 15 1000 UT. We report here observations of the intensity and spectrum obtained with an integration time of ∼30 min. They show that, at the beginning of this period, Cyg X-1 was more intense, had a steeper spectrum and was generally more active than has been observed during the past 2½yr by Copernicus1,2. Towards the end of the period the source seemed to be returning to its lower state.
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SANFORD, P., IVES, J., BURNELL, S. et al. Ariel V and Copernicus measurements of the X-ray variability of Cyg X-1. Nature 256, 109–111 (1975). https://doi.org/10.1038/256109a0
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DOI: https://doi.org/10.1038/256109a0
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