Orbital variability has been found in the X-ray hardness of the black hole candidate Cygnus X-1 during the soft/high X-ray state using light curves provided by the Rossi X-ray Timing Explorer ’ s All Sky Monitor .
We are able to set broad limits on how the mass-loss rate and X-ray luminosity vary between the hard and soft states .
The folded light curve shows diminished flux in the soft X-ray band at \phi = 0 ( defined as the time of of the superior conjunction of the X-ray source ) .
Models of the orbital variability provide slightly superior fits when the absorbing gas is concentrated in neutral clumps and better explain the strong variability in hardness .
In combination with the previously established hard/low state dips , our observations give a lower limit to the mass loss rate in the soft state ( \dot { M } < 2 \times 10 ^ { -6 } \mbox { M } _ { \odot } yr ^ { -1 } ) than the limit in the hard state ( \dot { M } < 4 \times 10 ^ { -6 } \mbox { M } _ { \odot } yr { -1 } ) .
Without a change in the wind structure between X-ray states , the greater mass-loss rate during the low/hard state would be inconsistent with the increased flaring seen during the high-soft state .