Stellar contributions to the hard X-ray galactic ridge

The number density of serendipitous sources in galactic plane Einstein Observatory IPC fields are compared with predictions based on the intensity of the HEAO 1 A-2 unresolved hard X-ray galactic ridge emission. It is concluded that it is unlikely that X-ray sources with 2-10 keV luminosities from about 8 x 10 to the 32nd to about 3 x 10 to the 34th ergs/s are dominant contributors to the hard X-ray galactic ridge. Their surfacea density is less than about 8 x 10 to the -4th/L(32)/sq pc. In particular, Be/neutron star systems such as X Per are not expected to be dominant contributors, both because the 2-10 keV luminosity is roughly 10 to the 33rd ergs/s and their scale height is too small. Lower luminosity stellar systems are likely to be major contributors to the ridge. RS CVn and CV systems with 2-10 keV luminosities between 2 x 10 to the 30th and 4 x 10 to the 32nd ergs/s contribute about 43 + or 18 percent.