Properties of X-ray quasars

A statistical analysis of the X-ray properties of 247 quasars observed by the Einstein Observatory in the 0.5–4.5 kev band is made. The main results are as follows. Among the various magnitude and redshift groups of 1619 known quasars, the proportion of X-ray sources is nearly constant. There is a strong correlation between the X-luminosity of Type-I Seyferts and the ratio of the equivalent widths of their Hg and [OIII] emission lines; the latter can be used as a X-luminosity indicator. The X-luminosity is correlated with both the optical luminosity and the radio luminosity above 2.5 GHz, suggesting that they have a similar emission mechanism and the regions of their emission are in that order. The X-luminosity is not correlated with either U-B or B-V. There is a weak correlation between the two colour indices.