Suzaku observations of six early type stars

We investigate spectra of six early type stars, four stars in Cyg OB2 association (Nos. 5, 8a, 9 and 12), ζ Oph and τ Sco, observed with Suzaku. Statistically good Suzaku-data provide us a unique tool for comparing their global spectral shape in X-ray band. We found that three Cyg OB2 stars, Nos. 5, 8a and 12, show similar high-energy-spectral shape to that of τ Sco, with high temperature (~1.5 keV) component. On the other hand, we found that ζ Oph shows a lack of the high energy component comparing to the other stars.