Z Cam in outburst during the ROSAT All-Sky Survey

We present the first X-ray observations of the dwarf nova Z Cam taken during outburst. ROSAT Survey observations show that Z Cam conforms to the pattern of X-ray behaviour seen in other dwarf novae, i.e., the quiescent hard X-ray emission is suppressed during outburst and replaced by extreme-ultraviolet emission which declines more rapidly than the optical flux. The timing of the hard X-ray suppression is measured with precision for the first time in any system.