Top panel: X-ray light curves observed by the Swift-XRT. The open and filled squares indicate the data of WT mode and PC mode of the Swift-XRT observations, respectively. Each energy flux in 2.0–10.0 keV is measured by time-resolved spectral analyses. Middle panel: the photon indices obtained by spectral fittings with the absorbed power-law model (Equation (1)). Bottom panel: the extra-galactic column density ﹩{N}_{{\rm{H}}}^{\mathrm{ext}}﹩ in units of ﹩{10}^{22}\;{\mathrm{cm}}^{-2}﹩.