Figure 7: Observed spectrum of the extragalactic XRB from HEAO-1 [61], Chandra [32], XMM [62], INTEGRAL [63], and Swift [64] data. The thick black solid line shows the population synthesis model for the XRB spectrum of Treister et al. [35]. Red, blue, and thin black solid lines show the contribution to this model from unobscured, obscured Compton thin, and CT AGN, respectively.