The orbital modulation in the radio emission of Cygnus X-1
  We present model lightcurves which have been created in order to explain the orbital modulation observed in the radio emission of Cyg X-1. We invoke variable absorption by the stellar wind as the black hole jet orbits around the OB companion star and find that a very simple model is able to reproduce the amplitudes and frequency dependence of the observed lightcurves. 
C. Brocksopp (Liverpool John Moores University, UK), R.P. Fender, G.G.   Pooley