HEAO-1 observations of a large number of cataclysmic variable stars demonstrated that most of these objects are not bright X-ray sources, even during their eruptive phases.

HEAO-1 scanned about 20 dwarf novae while they were undergoing optical outbursts, yet soft X-ray emission (0.18-0.43 keV) was detected only from SS Cyg and U Gem. The 3σ upper limits to the flux from the nondetected objects, several of which were observed by HEAO-1 during more than one outburst, range from 1 to 10% of U Gem’s mean flux of ∽ 1 × 10-10 erg cm-2 s-1. SS Cyg itself was detected during outburst at an intensity 20% of this value.