In the present paper, we have constructed a soft X-ray excess (SXE) sample from the sample of strong soft X-ray QSOs of Wilkes and Elvis (WE sample) by selecting those with column densities N_H_ less than the galactic column densities N_HG_. By adopting a model such that the X-ray spectral index is linearly dependent on the energy (ILDE model) instead of the pure power-law (PPL) model, we have obtained for most of the sources N_H_>= N_HG_ so N_H_ has got a physical meaning as the total effective hydrogen column density. We further determine the spectral indices α_0.3_ at 0.3 keV for the sources in the sample. It has been found that SXEs are common in the WE sample and that most of them are also strong SXE sources. From the N_H_ values of the 20 sources in our SXE sample, we discover a correlation between the N_H_ - N_HG_ value with the X-ray luminosity and with the optical luminosity. This shows that the N_H_ - N_HG_ value is mainly contributed from the intrinsic absorption by the gas in QSOs.
No takes yet. Share an insight, caveat, or question.
Zhou et al. (1992) studied this question.