THE CONTRIBUTIONS OF RSCVN SYSTEMS TO THE DIFFUSE-X-RAY BACKGROUND

We present comprehensive calculations of the contribution of RSCVn binaries to the diffuse X-ray background. We consider luminosity distribution functions derived from both optically selected volume-limited and X-ray selected flux-limited samples, use the Bahcall-Soneira galaxy model to describe the spatial distribution of stars in the Galaxy, and take into account anisotropic absorption by the interstellar medium. Our principal results are that RSCVn binaries provide approximately 16% to the observed low-latitude background at intermediate X-ray energies (1-2 keV), while in the 2-6 keV band their contribution to the total background amounts to approximately 6%, which however represents a approximately 27% contribution to the galactic ridge excess emission. This additional stellar component thus helps to fill up the absorption dip in the extragalactic background produced by absorption in the Galaxy and to isotropise the total M band background. However, our models of RSCVn systems are unable to account for the iron line observed in the galactic ridge.