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Orbital modulation and longer-term variability in the radio emission from Cygnus X-1

G. G. Pooley·R. P. Fender·C. Brocksopp
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Abstract

20 months of observations of the radio emission at 15 GHz from Cygnus X-1, starting in 1996 October, show variations at the binary period of 5.6 days, but with a phase offset from those at X-ray wavelengths. There are also longer-term variations on a time-scale of 150 days which are only loosely related to the soft X-ray flux. The source was in the hard/low X-ray state throughout this period. The mean 15-GHz flux density is 13 mJy, the radio spectrum is flat, and the semi-amplitude of the orbital modulation about 2 mJy. We discuss the possible origins of the modulation and the relationship to the soft X-ray emission.

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G. G. Pooley, R. P. Fender, C. Brocksopp. 1998-09-24. Orbital modulation and longer-term variability in the radio emission from Cygnus X-1. https://doi.org/10.1046/j.1365-8711.1999.02225.x

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