X-ray Study of the Intermediate-Mass Young Stars Herbig Ae/Be Stars

We present the ASCA results of intermediate-mass pre-main-sequence stars (PMSs), or Herbig Ae/Be stars (HAeBes). Among the 35 ASCA pointed-sources, we detect 11 plausible X-ray counterparts. X-ray luminosities of the detected sources in the 0.5–10 keV band are in the range of log LX ∼30−32 ergs s , which is systematically higher than those of low-mass PMSs. This fact suggests that the contribution of a possible low-mass companion is not large. Most of the bright sources show significant time variation, particularly, two HAeBes MWC 297 and TY CrA exhibit flare-like events with long decay timescales (efolding time ∼ 10−60 ksec). These flare shapes are similar to those of low-mass PMSs. The X-ray spectra are successfully reproduced by an absorbed one or National Research Council, 500 Fifth Street, NW, Washington, DC 20001, USA