Abstract
FROM May 1 to May 8, 1975, Cyg X-1 was observed with the instruments on board the Astronomical Netherlands Satellite (ANS). We report here the results of the measurements performed with soft and hard X-ray detectors of the Space Research Laboratory in Utrecht and the Center for Astrophysics in Cambridge, USA. Cyg X-1 underwent an upward transition in its intensity1, that seems to be the inverse of the downward transition seen by Uhuru in April 1971. The bulk of the increase occurs at low energy: between 1 and 2 keV, the intensity increased by a factor of 10 over the November 1974 intensity observed by ANS, while above 8 keV there is no significant change.
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HEISE, J., BRINKMAN, A., SCHRIJVER, J. et al. X-ray observations of Cyg X-1 with ANS. Nature 256, 107–108 (1975). https://doi.org/10.1038/256107a0
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DOI: https://doi.org/10.1038/256107a0
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