The Einstein X-ray Observatory Catalog of O-type stars

Abstract

Soft X-ray (0.2-3.5 keV) measurements for all normal, massive, O-type stars surveyed with the Einstein Observatory are presented as a catalog containing 89 detections and 176 upper bounds, together with a detailed discussion of the reduction process. Among the detections are 42 newly identified X-ray sources, several of them in heavily obscured regions. Values of L_x_/L_bol_, listed for most stars, range from 10^-5.44^ to 10^-7.35^; L_x_ spans more than 3 orders of magnitude, ranging from 1.5 x 10^31^ to 2 x 10^34^ ergs s^-1^. It is noted that at least 30% of O-type stars are variable in X-rays, but that there is little evidence for new objects whose X-ray emission might be significantly enhanced by accretion processes onto a neutron star.