ner_tags: O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-CelestialObject B-CelestialObject O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O O B-Wavelength O O O O O O O O O O O O O B-Wavelength O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O O O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O O O O O O O B-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O B-Wavelength O O O O O O O O O O O O O O O B-Telescope B-Instrument O O O O O O O O O B-Telescope O O O O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Wavelength O O O O B-Telescope O B-Telescope O O O O O O O O O O B-CelestialObject O B-CelestialObject B-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O
tokens: large sample of AGNs and obtain some different results. (1) A few sources exhibit a hint of saturation at high flux levels, but about half of the sources do not show a clear evidence of saturation in our data (e.g. Ark120, Mrk110, Figs A5 and B3 ). (2) Different sources follow different tracks (i.e. different slopes of the correlation) in the L X / L Edd diagram rather than a common relation (i.e. a single slope of the correlation). (3) Using the sample of AGNs instead of individual source, we can explore the spectral evolution in a much larger X-ray Eddington ratio range (4 orders of magnitude, Fig. 1 ). (4) We introduce the slope of the correlation to parametrize the increase speed of as a function of flux, and find for an anticorrelation between and the X-ray Eddington ratio. Globally, the increasing tendency of with increasing X-ray luminosity becomes slower, but there is no saturation effect observed even when the X-ray Eddington ratio increases by four orders of magnitude (Fig. 1 ). 4 DISCUSSION It is well known that the observed is governed by the absorption, the reflection effects, and the Comptonization process itself. The X-ray flux can change significantly within a time-scale as short as 10 3 10 4 s; however, neither the column density nor the covering factor is expected to vary so fast. On the other hand, the variation of X-ray flux can affect the ionization state and the opacity of absorber, resulting in variable absorption. In this way, the observed increases with increasing the X-ray flux, but the derived relation is much shallower than the data of most sources (Sobolewska Papadakis 2009 ). Moreover, such absorption effect should be prominent at high luminosity, that is in conflict with the anticorrelation between and the X-ray Eddington ratio shown in Fig. 2 . The reflection component could offer a significant fraction of X-ray emissions, and tend to flatten the spectrum below 10keV, reducing the observed . However, the reflection is unimportant in the power-law fitting with the RXTE /PCA data due to their low energy resolution. Investigating the RXTE data of 10 AGNs (all in our sample), Sobolewska Papadakis ( 2009 ) argued that a constant reflection component plus a power-law component, which is variable in flux but constant in profile, failed to account for the spectral evolution. It is unclear whether the spectral softening behaviour can be interpreted as the decreasing of the relative contribution of the reflection component with increasing the X-ray flux. Recently, observations with XMMNewton and NuSTAR have been made on several objects in our sample (e.g. MCG-6-30-15 and Ark120; Parker etal. 2014 ; Porquet etal. 2018 ), and these data have sufficient statistics and spectral resolution to separate out the intrinsic power-law and reflection components. A quantitative estimation on the influence of the reflection effect at different flux levels could be accomplished with next generation of X-ray missions in the future (e.g.