Top panel: average 2009 Long Look pn (black), MOS1 (red), and MOS2 (blue) spectra modeled with a power-law emission absorbed by the Galactic interstellar medium, along with the residuals to the model, scaled by the error bar. Bottom panel: spectral residuals to the power-law model for the other three epochs: Dec. 2008 (green triangles), Jun. 2008 (red circles), and Dec. 2004 (blue squares); the data have been rebinned for visual purpose only to respectively 5, 5, and 7σ.