We present ASCA observations of the dwarf nova Z Camelopardalis during outburst and during a transition from quiescence to another outburst .

At the beginning of the transition the X-ray count rate was an order of magnitude higher and the spectrum much harder than during the outburst .
As the transition progressed , the spectrum remained hard as the X-ray flux decreased by a factor of 3 , with no spectral softening .

Spectral modelling reveals an optically-thin , high-temperature component ( kT \approx 10 keV ) which dominates the transition observation and is also observed during outburst .
This is expected from material accreting onto the white dwarf surface .
The outburst spectra require additional emission at lower temperatures , either through an additional discrete temperature component , or a combination of a cooling flow model and an ionised absorber .

Fits to both observations show large amounts of absorption ( N _ { H } = 8 - 9 \times 10 ^ { 21 } cm ^ { -2 } ) , two orders of magnitude greater than the measured interstellar value , and consistent with UV measurements of the outburst .
This suggests that a disk wind is present even in the earliest stages of outburst , possibly before the outburst heating wave has reached the boundary layer .