ROSAT X-RAY OBSERVATIONS OF HYBRID STARS

We report on X-ray observations of four hybrid stars with the position-sensitive proportional counter (PSPC) on the Rontgensatellit (ROSAT). Three of our program stars, beta-Ind, mu-UMa, and gamma-Aql were detected as X-ray sources for the first time. For one star, gamma-Aql, the detection is of low significance, while for the other two stars, beta-Ind and mu-UMa, we have collected enough counts to accumulate-for the first time for a hybrid star-a pulse height spectrum and perform a spectral analysis of the pulse height distribution. The dominant emission feature component for both stars is located at temperatures of log T approximately 6.4. Our data are, however, of insufficient signal-to-noise ratio to assess the presence of even hotter temperature components or the possible self-absorption by the also present cool winds in these stars. For the remaining star in our sample, iota-Aur, we report a sensitive upper limit.