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

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.

Accepted for publication in MNRAS

References in corpus (3)

• The variable radio emission from GRS 1915+105
• The 1996 Soft State Transitions of Cygnus X-1
• The Orbital Period of HDE226868/Cyg X-1

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