Early-Type Stars:  Then
					Harnden et al., 1979, Ap. J., 234, L51.
	* Early-type stars were not known to be X-ray sources prior to the launch of the Einstein Observatory. * This class of sources was “discovered” serendipitously through extended observations of the binary Cyg X-3.  Five of the brightest O and B stars in the nearby VI Cygni association showed up as point sources. * They could only infer spectral properties using broadband countrates.  They typically found: T ~ 5 - 10 MK, NH ~ 1022 cm-2, and LX ~ few x 1033 ergs/s ~ 10-4 LV.