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   PR # 12120
    The X-ray production mechanism in O stars has been a subject of
    debate for more than a decade. The basic discriminator between the
    proposed models of X-ray production is determining the spatial
    location of the X-ray source within the surrounding stellar wind. To
    determine the X-ray location, it is imperative to ascertain the indiv
    idual contributions of the ISM and wind absorption components. The
    current problem is that the available X-ray data are not sufficient
    to resolve this issue. Therefore, we propose ASCA SIS observations of
    a few selected O stars. Due to the higher energy resolution and sensi
    tivity, SIS observations have the potential to place very strong cons
    traints on the existence and strength of the stellar wind absorption
   component.
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