We have observed 14 Herbig Ae/Be stars in X-rays with the ROSAT PSPC (
0.1 - 2.4 keV). In addition, we obtained data from the ROSAT archive f
or 7 Herbig Ae/Be stars. As a result, 11 of the 21 Herbig Ae/Be stars
studied here have been detected as X-ray sources, among them AB Aur, H
R5999/6000, and Z CMa. This is surprising, since Ae/Be stars, being pr
edominantly radiative, are unlikely to sustain dynamo magnetic fields
and coronal heating. We have investigated possible correlations betwee
n the X-ray luminosity and other stellar parameters like L(bol), spect
ral type, stellar rotation and winds. We suspect that the origin of th
e X-ray emission is likely to be related to the stellar wind, although
other explanations (e.g. unresolved T Tauri companions) are also disc
ussed. Some Ae/Be stars are known to be the exciting sources of high-v
elocity jets, but none of the jets themselves were detected in X-rays.
In several cases, the X-ray images revealed a small cluster of source
s, presumably lower mass pre-main-sequence objects that surround the m
ore massive Ae/Be stars.