  Chandra High Energy Transmission Grating Spectrometer (HETGS) observations of
the extremely luminous and violent X-ray binary Cir X-1 reveal many X-ray
emission lines showing broad P Cygni profiles. These are from H-like and
He-like ions of Ne, Mg, Si, S, Ar, and Fe. The lines originate in a
high-velocity (up to 2000 km s^-1) outflow, which may be an accretion disk
wind. Cir X-1 has a radio jet, and during some periastron passages of the
neutron star (orbital phase = 0.0), it flares at radio, infrared and X-ray
wavelengths. The X-ray P Cygni profiles were observed during this phase, where
we also expect the strongest mass transfer from the companion star. We present
new results on the time variability of the P Cygni profiles and discuss their
general importance.
