Abstract
Results of the analysis of four balloon observations of Cyg X-1 in the energy range 20–200 keV are reported. Long term time variability of the flux is confirmed and is estimated to amount to a factor 1.5–2. The source appears to remain in a state of lower flux for longer times. No obvious correlation with the low energy behaviour following the transition detected by Uhuru is found.
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Frontera, F., Fuligni, F. & Cavani, C. Long term variability of Cyg X-1 in hard X-rays. Astrophys Space Sci 32, 197–203 (1975). https://doi.org/10.1007/BF00646225
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DOI: https://doi.org/10.1007/BF00646225