The ratio of X-ray-to-optical luminosity for active galactic nuclei

It is shown that the apparent enhancement of the average ratio of X-ray to optical luminosity for Seyfert 1 nuclei, in comparison with radio quiet QSOs, may be largely, if not totally, due to internal reddening. Estimates of the average optical to X-ray energy index, αsub(ox), for five independent samples covering, altogether, over three orders of magnitude in optical luminosity, are all consistent with α-barsub(ox) approx.= 1.55 and a dispersion σ approx.= 0.15. A comparison of optical and X-ray counts adds support to this conclusion. (author)