EINSTEIN X-RAY OBSERVATIONS OF HERBIG AE BE STARS/

We have investigated the X-ray emission from Herbig Ae/Be stars, using the full set of Einstein IPC observations. Of a total of 31 observed Herbig stars, 11 are confidently identified with X-ray sources, with f our additional dubious identifications. We have used maximum likelihoo d luminosity functions to study the distribution of X-ray luminosity, and we find that Be stars are significantly brighter in X-rays than Ae stars and that their X-ray luminosity is independent of projected rot ational velocity v sin i. The X-ray emission is instead correlated wit h stellar bolometric luminosity and with effective temperature, and al so with the kinetic luminosity of the stellar wind. These results seem to exclude a solar-like origin for the X-ray emission, a possibility suggested by the most recent models of Herbig stars' structure, and su ggest an analogy with the X-ray emission of O (and early B) stars. We also observe correlations between X-ray luminosity and the emission at 2.2 mu m (K band) and 25 mu m, which strengthen the case for X-ray em ission of Herbig stars originating in their circumstellar envelopes.