line versus the X-ray luminosity obtained simulating a torus with an equatorial column density of $\log N_{\rm\,H}^{\rm\,T}=23.1$ and a covering factor decreasing with the luminosity. The $\theta_{\mathrm{OA}}-L_{\mathrm{X}}$ relationship used here is that of @Hasinger:2008ve (see Fig.\[fig:tor\_CFL2\]). The relations of @Bianchi:2007vn (black dashed line) and @Shu:2012fk ([-@Shu:2012fk]; blue line, obtained averaging different observations of the same source) are also shown for comparison (see also Table\[tab:XBEref\]). The normalization of the relation of @Bianchi:2007vn has been fixed to an arbitrary value for comparison.[]{data-label="fig:IT_hasinger"}](ITeff_hasinger.ps){width="9cm"}

![image](slope_NH_Syrange.ps){width="9cm"}

![image](interc_NH_Syrange.ps){width="9cm"}

To estimate the influence of the decreasing covering factor of the torus on the equivalent width of the iron line, we simulated, using the physical torus models, a large number of spectra using the $\theta_{\mathrm{OA}}-L_{\mathrm{X}}$ relationships reported in Eq.\[Eq:Hasinger\]-\[Eq:Maiolino\]. Using the three different $\theta_{\mathrm{OA}} - L_{\mathrm{X}}$ relationships, we extrapolated the value of $\theta_{\mathrm{OA}}$ for each luminosity bin ($\Delta \log L_{\mathrm{X}}=0.01$). We fixed the equatorial column density of the torus $N_{\rm\,H}^{\rm\,T}$ to 26 different values, spanning between $10^{22.5}\rm\,cm^{-2}$ and $10^{25}\rm\,cm^{-2}$, with a step of $\Delta \log N_{\rm\,H}^{\rm\,T}=0.1$. To simulate an unabsorbed population, similarly to what is usually used to determine the X-ray Baldwin effect, for each value of $L_{\rm\,X}$ and $N_{\rm\,H}^{\rm\,T}$ we considered inclination angles $\theta_{\,\mathrm{i}}$ between $1^{\circ}$ and 